Guided transport path correction

ABSTRACT

A printer deposits material onto a substrate as part of a manufacturing process for an electronic product; at least one transported component experiences error, which affects the deposition. This error is mitigated using transducers that equalize position of the component, e.g., to provide an “ideal” conveyance path, thereby permitting precise droplet placement notwithstanding the error. In one embodiment, an optical guide (e.g., using a laser) is used to define a desired path; sensors mounted to the component dynamically detect deviation from this path, with this deviation then being used to drive the transducers to immediately counteract the deviation. This error correction scheme can be applied to correct for more than type of transport error, for example, to correct for error in a substrate transport path, a printhead transport path and/or split-axis transport non-orthogonality.

This application is a divisional of U.S. Utility patent application Ser.No. 15/828,335, filed on Nov. 30, 2017 on behalf of first-named inventorEliyahu Vronsky for “Guided Transport Path Correction which in turn is acontinuation of U.S. Utility patent application Ser. No. 15/642,188,filed on Jul. 5, 2017 on behalf of first-named inventor Eliyahu Vronskyfor “Guided Transport Path Correction, which in turn claims the benefitof U.S. Provisional Application No. 62/489,768, filed on Apr. 25, 2017on behalf of first-named inventor Digby Pun and U.S. ProvisionalApplication No. 62/359,969, filed on Jul. 8, 2016 on behalf offirst-named inventor Digby Pun, each titled “Transport Path CorrectionTechniques And Related Systems, Methods And Devices,” and U.S.Provisional Patent Application No. 62/459,402, filed on Feb. 15, 2017 onbehalf of first-named inventor David C. Darrow for “Precision PositionAlignment, Calibration and Measurement in Printing And ManufacturingSystems;” each of these applications is hereby incorporated byreference. This disclosure also incorporates by reference the followingdocuments: U.S. Pat. No. 9,352,561 (U.S. Ser. No. 14/340,403), filed asan application on Jul. 24, 2014 on behalf of first inventor Nahid Harjeefor “Techniques for Print Ink Droplet Measurement And Control To DepositFluids Within Precise Tolerances;” US Patent Publication No. 20150360462(U.S. Ser. No. 14/738,785), filed as an application on Jun. 12, 2015 onbehalf of first inventor Robert B. Lowrance for “Printing SystemAssemblies and Methods;” US Patent Publication No. 20150298153 (U.S.Ser. No. 14/788,609), filed as an application on Jun. 30, 2015 on behalfof first-named inventor Michael Baker for “Techniques for ArrayedPrinting of a Permanent Layer with Improved Speed and Accuracy;” andU.S. Pat. No. 8,995,022, filed as an application on Aug. 12, 2014 onbehalf of first-named inventor Eliyahu Vronsky for “Ink-Based LayerFabrication Using Halftoning To Control Thickness.”

BACKGROUND

Certain types of industrial printers can be applied to precisionmanufacture, for example, to the fabrication of electronic devices.

To take one non-limiting example, ink jet printers can be used todeposit one or more super-thin layers of an electronic display device ora solar panel device. The “ink” in this case differs from conventionalnotions of ink as a dye of a desired color, and instead can be anorganic monomer deposited as discrete droplets that spread somewhat andmeld together, but that are not absorbed and instead retain a deliberatelayer thickness that helps impart structural, electromagnetic or opticalproperties to the finished device; the ink is also typicallydeliberately made to be translucent with a resultant layer being used togenerate and/or transmit light. A continuous coat of the ink depositedby the printing is then processed in place (e.g., cured usingultraviolet light, or otherwise baked or dried) to form a permanentlayer having a very tightly regulated thickness, e.g., 1-10 microns,depending on application. These types of processes can be used todeposit hole injection layers (“HILs”) of OLED pixels, hole transferlayers (“HTLs”), hole transport layers (“HTLs”), emissive or lightemitting layers (“EMLs”), electron transport layers (“ETLs”), electroninjecting layers (“EILs”), various conductors such as an anode orcathode layer, hole blocking layers, electron blocking layers,polarizers, barrier layers, primers, encapsulation layers and othertypes of layers. The referenced materials, processes and layers areexemplary only. In one application, the ink can be deposited to create alayer in each of many individual electronic components or structures,for example, within individual microscopic fluidic reservoirs (e.g.,within “wells”) to form individual display pixels or photovoltaic celllayers; in another application, the ink can be deposited to havemacroscopic dimensions, for example, to form one or more encapsulationlayers cover many such structures (e.g., spanning a display screen areahaving millions of pixels).

The required precision can be very fine; for example, a manufacturer'sspecification for fabricating a thin layer of an organic light emittingdiode (“OLED”) pixel might specify aggregate fluid deposition within apixel well to a resolution of a picoliter (or to even a greater level ofprecision). Even slight local variations in the volume of depositedfluid from specification can give rise to problems. For example,variation in ink volume from structure-to-structure (e.g.,pixel-to-pixel) can give rise to differences in hue or intensitydifferences or other performance discrepancies which are noticeable tothe human eye; in an encapsulation or other “macroscopic” layers, suchvariation can compromise layer function (e.g., the layer may notreliably seal sensitive electronic components relative to unwantedparticulate, oxygen or moisture), or it can otherwise give rise toobservable discrepancies. As devices become smaller and smaller theseproblems become much more significant. When it is considered that atypical application can feature printers having tens-of-thousands ofnozzles that deposit discrete droplets each having a volume of 1-30picoliters (“pL”), and that manufacturing process corners for theprintheads can lead to inoperative nozzles and individual error in anyof droplet size, nozzle location, droplet velocity or droplet landingposition, thereby giving rise to localized ink volume deliveryvariation, it should be appreciated that there are very great challengesin producing thin, homogeneous layers that closely track desiredmanufacturing specifications.

One source of error in achieving fine precision relates to the use ofmechanical components in the fabrication processes relative to the scaleof products being manufactured. As a non-limiting example, most printershave mechanical conveyance systems that move one or more printheads, asubstrate, or both in order to perform printing. Some printers alsofeature conveyance systems for rotating or offsetting components (e.g.,moving or rotating printheads to change effective pitch betweennozzles); each of these conveyance systems can impart fine mechanical orpositioning error that in turn can lead to non-uniformity. For example,even though these conveyance systems typically rely on high-precisionparts (e.g., precision tracks or edge guides), they can still impartjitter or translational or rotational inaccuracy (e.g., such asmillimeter, micron or smaller scale excursions in the transport path)that makes it difficult to achieve the required precision and uniformitythroughout the transport path lengths used for manufacture. To providecontext, an apparatus used to fabricate large size HDTV screens mightfeature a “room sized” printer which is controlled so as to deposit anultra-thin material layer on substrates meters wide by meters long, withindividual droplet delivery planned to nanometer-scale coordinates; thetransport paths in such an apparatus can be meters in length. Note thatthere are many other mechanical components that can give rise to someform of error in such a system, for example, transport path systems usedto interchange printheads, camera assemblies to align or inspect asubstrate, and other types of moving parts. In such a system, even veryfine precision mechanical parts can create excursions that affect thenanometer-scale coordinates just referenced. Thus, the required layersbecome thinner and thinner, and the require precision becomes smallerand smaller relative to the product being fabricated, it becomes evenmore imperative to carefully control and/or mitigate sources ofpotential positional error.

There exist some conventional techniques for reducing positional andtranslational error generally in these types of fabrication systems.First, a substrate can be coarsely-aligned with printer transport andthen manually fine-aligned (potentially repeatedly during thefabrication process); such a process is time-consuming, i.e., itgenerally impedes the goal of having an automated, fast, assembly-linestyle process for producing consumer products. It is also generallyquite difficult to obtain the required micron- or nanometer-precisionwith such a manual process. There also are some errors that cannot beadequately addressed with such a technique, for example, errors causedby transport path discrepancies, as just introduced above (e.g., errorwhich manifests itself after a substrate has been aligned). As a secondexample, US Patent Publication No. 20150298153 relates to processes thatmeasure fine positional and/or rotational errors in substrate positionand that correct for those errors in software, for example, byreassigning which nozzles are used to print or by otherwise changing thenozzle drive waveforms which are used to fire nozzles; in other words,generally speaking, these techniques attempt to “live with” finepositional and rotational error (thereby preserving print speed) andthey then attempt to adjust which nozzles are used and when and howthose nozzles are electronically controlled, so as to remedy error(e.g., using a preplanned raster without having to re-adjust scan pathsdependent on error). However, despite the utility of compensating foralignment error in software, the measuring and accounting for this errorand re-computing firing assignments for thousands of nozzles in softwarecan take substantial computing resources and time.

What are needed are additional techniques for correcting for motion,rotation and position error in mechanical systems in a manufacturingapparatus. Still further, what are needed are techniques for correctingfor error in a moving component of a manufacturing system in order tosimulate an “ideal” edge or transport path. Such techniques, if appliedto precision manufacturing processes, especially printing systems of thetype described, would reduce the need for substantial computingresources and time to re-render raster control data and, overall, leadto a simpler and/or faster and/or more accurate print process. Thepresent invention addresses these needs and provides further, relatedadvantages.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a substrate 103 as it is transported through anindustrial printing system along a transport path 107; at its rightside, FIG. 1 shows the substrate at two hypothetical positions (103′ and103″) with respective rotation and translation error (x, Δy, and Δθ).Transport path error and associated substrate rotation and translationerror is seen as exaggerated relative to drawing scale, to assist withexplanation.

FIG. 2A is a schematic view of a system 201 that dynamically correctsfor mechanical error. A first component 203 travels along a transportpath 206 (generally aligned with the “y” axis in this example), andmirrors 211/212 and sensors 208/209 detect deviation from an opticalguide 202 (e.g., a laser beam); during travel of the first component,transducers 216 and 217 are automatically driven in response to signalsfrom sensors 208/209 to equalize the deviation (e.g., in one or moredimensions, such as x, z and/or θ), such that a second component 205follows an ideal path, notwithstanding the mechanical error.

FIG. 2B is a flow chart associated with correcting positional and/orrotational error as a transported component is advanced along atransport path.

FIG. 3A is a schematic diagram showing one or more transducers thatperform fine mechanical adjustments to correct for errors referenced inconnection with FIG. 1 (i.e., in this example, as part of a “gripper”that advances the substrate); as noted, an optical guide such as a lasersource 319 can be used to define a desired path, with deviation fromthis path being sensed by one or more sensors 320. One or moretransducers “T” are driven as a function of this deviation, with theresult that the substrate (in this example) travels a “perfectlystraight” or “jitter free” transport path.

FIG. 3B depicts a transport path 107 having mechanical imperfections,just as with FIG. 1; however, in this case, transducers “T,” such asintroduced relative to FIG. 3A, are used to perform fine tuningadjustment for the substrate position and/or orientation as the gripperadvances on the path 107. The result is that the substrate now movesaccording to “ideal” motion (e.g., a perfectly straight “ideal” edgeand/or jitter free path), as represented by a virtual straight edge 323.

FIG. 3C is similar to FIG. 3B, in that it shows use of transducers “T”to correct for transport path error. However, in this case, error alsopotentially arises from a second transport path 356, in this case,manifested as the non-ideal position or orientation of a printhead (orcamera or other assembly) as it is transported in the general directionof arrows 354.

FIG. 3D is similar to FIG. 3C in that it depicts motion of a printheadalong an edge or track 356 but, as illustrated, a printhead assembly nowalso has its own optical guide 371 and transducer assembly(ies) toprovide for fine tuning positional and rotational corrections thatmitigate error in the edge or track 356; the result is that theprinthead now also effectively travels a virtual “ideal” path 325 (or369, as will be discussed below).

FIG. 3E is similar to FIG. 3C in that it depicts motion of a printheadalong an edge or track 356; however, although the printhead transportpath has an optical guide, corrections to match printhead jitter areinstead applied by a transducer-based error correction system associatedwith another transport path, in this case, transducers associated withthe gripper.

FIG. 3F is an illustrative diagram showing a mechanism for correctingfor transport path error, for example, by performing compensatingcountermotions (or other error mitigation) in up to six differentdegrees of freedom (e.g., potentially including three translationaldegrees of freedom, as well as yaw, pitch and/or roll).

FIG. 4A provides a plan view of a substrate, and shows a raster orscanning process; a shaded area 407 represents a single scan path, whilea clear area 408 represents another. As indicated by a dimensionallegend in the FIG., in this example, an “x” axis corresponds to across-scan dimension while a “y” axis corresponds to an in-scandimension.

FIG. 4B provides a plan, schematic view of a fabrication machine thatincludes multiple modules, one of which (415) features a printer withina controlled atmosphere.

FIG. 4C is a block diagram that illustrates one method 431 ofdynamically correcting transport path error in an industrial printingsystem.

FIG. 5 is an illustrative view showing a series of optional tiers,products or services that can each independently embody techniquesintroduced herein; for example, these techniques can be embodied in theform of software (per numeral 503), or as printer control data (pernumeral 507), to be used to control a printer to print on a substrate orotherwise to correct for error, or as a product made in reliance onthese techniques (e.g., as exemplified by numeral 511, 513, 515 or 517).

FIG. 6A is a detail, perspective view of one embodiment of an industrialprinter, such as the printer inside the printing module of FIG. 4B.

FIG. 6B is a detailed perspective view of an embodiment of a gripper.

FIG. 6C is a close-up, perspective view of a transducer assembly fromthe gripper of FIG. 6B.

FIG. 6D is a close-up, perspective view of a floating, mechanical pivotassembly from the gripper of FIG. 6B.

FIG. 6E is a schematic side view of the error correction systemrepresented by FIGS. 6B-6D, with an emphasis on design of the floating,mechanical pivot assembly.

FIG. 7A shows an embodiment 701 where an optical guide 702 is used toensure straight motion of a gripper 703 and substrate 704.

FIG. 7B shows an embodiment 713 where a laser source and/or lightredirection optics are mounted to a gripper's offsettable component, orother element being transported.

FIG. 7C shows an embodiment 719 where a sensor 720 is used to calibratea light source 721, e.g., so as to detect and/or correct for path error722 relative to an intended path 723.

FIG. 7D shows an embodiment 727 where a light source 728 is improperlyaligned; unlike the embodiment of FIG. 7C, however, deviation between anerroneous optical path 729 and a correct optical path 730 is correctedfor electronically, by using transducers (represented by arrow-icons732A/732B) to perform compensating offsets. Signals to control theseoffsets can be stored in digital memory and retrieved during systemoperation or otherwise added to dynamic corrections as a function oftransport path position, such that a transported component follows thecorrect path 730.

FIG. 7E shows an embodiment 735 that implements a zero-target controlloop; sensors 736A/736B dynamically detect deviation from a desired pathin one or more dimensions (in this case represented by deviation between“cross-hairs” 737A/737B and a beam 738 from a laser source 739); amotion controller 741 provides feedback to drive transducers 742A/742Bso as to always drive error to zero.

FIG. 7F shows an embodiment 745 where transducers 746A/746B are drivento maintain a transported object (e.g., a gripper 747 and substrate 748)as always level relative to an optical guide 749. In this case, sensors750A/750B detect deviation of the substrate and/or part of the gripperfrom the optical guide 749, and drive two transducers 746A/746B toequalize jitter in height, or to otherwise precisely control height.

FIG. 7G shows an embodiment 755 which uses two parallel conveyancesystems 756A/756B for a given direction of transport. In this case, eachconveyance system has its own optical guide 757A/757B and transducercompensation system 759A/759B. One of the conveyance systems 7566 alsomounts another light source 765, which generates an optical guide 766,used to align and synchronize the two conveyance systems 756A/756B. Asignal from a detector 767 on the second conveyance system 756A is fedto a motion controller 763 so as to maintain synchronization between theconveyance systems.

FIG. 7H shows an embodiment 771 where two conveyance systems 772 and 773each have their own source 774/775 and motion controller 780/781. Theresult is that errors are corrected transparently to general systemmotion control, such that each motion controller 780/781 can receiverespective (absolute position coordinate) command signals 782/783 toestablish proper position relative to a system coordinate referencesystem.

FIG. 7I shows an embodiment 787 where two conveyance systems 788/789each have their own source 790/791 and sensor pairs 792A,B/793A,B, butwhere only one system has a transducer-based error correction system(794A/B); in this case, a motion controller 795 generates transducercontrol signals 796A/796B so that one of the conveyance systems (789)compensates for error associated with other conveyance system 788.Non-motion errors, such as error in alignment of the optical guide foreither conveyance system and/or non-orthogonality between the conveyancesystems, can also be corrected.

FIG. 8A is a cross-sectional view of an assembly that uses two differentsets of transducers “T” to correct for error in two or more dimensions.

FIG. 8B is a cross-sectional view of another assembly that uses twodifferent sets of transducers “T” to correct for error in two or moredimensions.

The subject matter defined by the enumerated claims may be betterunderstood by referring to the following detailed description, whichshould be read in conjunction with the accompanying drawings. Thisdescription of one or more particular embodiments, set out below toenable one to build and use various implementations of the technologyset forth by the claims, is not intended to limit the enumerated claims,but to exemplify their application. Without limiting the foregoing, thisdisclosure provides several different examples of techniques formitigating transport path error in a manufacturing apparatus or printer,and/or for fabricating a thin film for one or more products of asubstrate as part of a repeatable print process. The various techniquescan be embodied in various forms, for example, in the form of a printeror manufacturing apparatus, or a component thereof, in the form ofcontrol data (e.g., precomputed correction data or transducer controldata), or in the form of an electronic or other device fabricated as aresult of these techniques (e.g., having one or more layers producedaccording to the described techniques). While specific examples arepresented, the principles described herein may also be applied to othermethods, devices and systems as well.

DETAILED DESCRIPTION

This disclosure provides improved techniques for correcting transportpath error and/or for fabricating a layer on a substrate with a highdegree of positional accuracy. In one embodiment, these techniques areapplied to a manufacturing apparatus or system that produces a layer ofan electronic display, a solar panel or another electronic device or,indeed any other type of precision device or product. The manufacturingsystem or fabrication system includes a conveyance system and acomponent will be guided along a transport path to assist withmanufacturing. The path length is typically quite long relative to therequired positioning precision. In a typical implementation, forexample, the conveyance path length can be meters, but the requiredpositioning can be micron-scale or even finer (e.g., nanometer-scale orfiner). To assist with precise positioning, one or more sensors are usedto detect deviation between the component and an optical beam, in one ormore dimensions. Deviation detected by the one or more sensors is thenused to derive position correction signals which are fed to one or moretransducers and used to offset the deviation, with the result that thecomponent tracks the optical path notwithstanding fine mechanical errorassociated with the transport path. In one embodiment, the one or moresensors provide feedback that causes the transducers to always“zero-out” positional and rotational error.

More specifically, these techniques can optionally be applied to aprinter used to fabricate electronic products where the printer depositsmaterial onto a substrate at precise coordinates. The conveyance systemin this context can be any mechanical system used by the printer, forexample, a gripper used to advance a substrate, a printhead motionsystem used to transport a printhead (e.g., orthogonally to motion of agripper), a camera conveyance system, a fly-height or printhead heightadjustment system, and other types of assemblies as well. In theimmediately ensuing discussion, an example will be narrated where thesetechniques are applied to gripper path adjustment; it should beunderstood that the techniques described herein are not limited to agripper conveyance system, nor are they limited to the context ofprinters in general. Conversely, it should also be understood that thesetechniques may optionally be applied to two or more conveyance systemsor transport systems in a manufacturing system, such as to control forany of x, y and/or z position, or associated rotational degrees offreedom, as desired. In one example discussed below, these techniquesare applied independently to each of gripper and printhead transportpaths, and are used in concert with a position feedback system for eachtransport path, in order to provide for precise positioning in x, yand/or z axes and in order to ensure coordinate system orthogonality andprecise position control in a printing system.

In one example, a glass substrate meters long and meters wide isintroduced into a “room-sized” printer, where the printer will printindividual droplets of “ink” at very precise coordinates (e.g., atprecise nanometer or sub-nanometer coordinates). Two conveyance systemsare used to position droplets, including a “gripper” which advances thesubstrate back-and-forth along a “fast” or “in-scan” direction, and aprinthead conveyance system which moves the printhead in a “slow” or“cross-scan” direction (e.g., the printhead is repositioned in betweenensuing scans so that printing occurs in a swath as the substrate movesunder the printhead). In variations, both systems can be movedsimultaneously, or the printhead or substrate can be stationary whilethe other moves in two or more dimensions. The droplet landing locationsare selected such that deposited droplets meld together on the glasssubstrate and provide gapless area coverage, so as to typically form aliquid coat without pinholes, gaps or other defects. The “ink” differsfrom traditional notions of ink for graphics printers and is typically arelatively viscous material (e.g., an organic monomer) that is colorlessor, alternatively stated, where native color of the material isunimportant; the ink is typically not absorbed and spreads only to alimited extent, such that the finished layer provides aspecifically-desired layer thickness or other specifically-desiredelectrical, magnetic, light-generating, structural or similar property.For example, the ink can in one embodiment be an organic monomer, wherea deposited coat (once droplets meld adequately) is then cured usingultraviolet light to form a polymer layer. The liquid coat, once formed,is then hardened, dried, cured, developed, or otherwise processed(“processed”) so as to form a permanent or semi-permanent layer of anelectronic product being fabricated on the glass substrate. Thesetechniques can be used to deposit light generating layers of individualpixels of electronic displays, encapsulation layers, and potentiallyother types of layers; for example, the techniques disclosed herein canbe applied to a wide variety of manufacturing processes, includingwithout limitation, to the deposition of precision coatings for “smartwindows” and other types of electronic, optical, or other devices. Notethat when used to form layers of precision electronic components (e.g.,micron- or nanometer-scale structures), each of the droplets in theforegoing examples must typically be deposited at very fine positionalcoordinates, e.g., too much or two little ink, or poorly positiondroplets can result in defective or suboptimal components. Whileprecision mechanical parts (e.g., tracks or edge guides) are used tohelp ensure accurate motion, these systems can still result inmechanical jitter that disrupts proper droplet placement.

In embodiments herein, to correct for this issue, a conveyance system(e.g., a gripper) can have two components including a first (or“track-guided”) component that moves along the conveyance path, and asecond (or “offsettable”) component, with one or more transducers beingused to offset the second component relative to the first. For example,the first component follows a track, while the second component mounts avacuum chuck that is used to engage the substrate; in other embodiments,other technologies can be used to engage and/or transport the substrate.As the first component experiences jitter and error, this error isdetected and used to drive the transducers, which cause the secondcomponent to offset the error such that the substrate travels an idealpath. In one embodiment, this is achieved by using a laser beam and/oroptics and/or a detector to mark an ideal path, with the secondcomponent mounting one or more of these optical components in a mannerso as to detect deviation of the second component from this marked,ideal path. The detected deviation is used to immediately drive thetransducers to counteract that deviation. In one implementation, asimple two-cell detector can be used to detect path deviation in onedimension, while in another implementation, a four-cell or morecomplicated design can be used to detect error in two or moredimensions; for example, in the context of the example just presented,the glass substrate can be supported on an air bearing (i.e., above agas floatation table) while the gripper can use suction to selectivelyengage and then to transport the substrate; the gripper's “secondcomponent” in one embodiment can be offset in the cross-scan dimension,as well as for height so as to match a fly-height of the substrate abovethe air floatation table (or otherwise to levelize the gripper).Naturally, other implementations will occur to those of ordinary skillin the art; as noted above, the techniques described herein can beapplied to a wide range of manufacturing and/or conveyance systems(e.g., application to a printer, gripper, printhead or similarcomponents are to be considered “optional”).

Note that whatever the source of the error (e.g., whether attributed tothe conveyance system as “repeatable” error or otherwise), thetechniques described herein immediately correct position of the thingbeing transported so that it experiences ideal motion, at least in oneor more dimensions orthogonal to the direction of transport. Thesetechniques are especially useful where precise positional and/ororientation control is desired, e.g., in an assembly-line style process,where each substrate or each product can experience fine repeatable ornon-repeatable position and/or orientation error.

To correct for and/or mitigate error, in one embodiment,fine-positioning transducers are driven without a fixed pivot point tocounteract the mechanical imperfections. These transducers perform finetuning of substrate position and/or orientation, and thereby counteractthe effects of the mechanical imperfections in at least one dimension.In this manner, although the conveyance system (e.g., the gripper,substrate, printhead, camera or other transport path) continues to becharacterized by mechanical imperfections, motion of the substrateand/or printhead is made to approximate ideal travel. In one embodiment,a transport path is substantially linear and transport substantiallyoccurs along a first dimension (e.g., the “y”-dimension) while two ormore transducers each independently apply linear offsets in anindependent dimension (for example, the “x”-dimension). Driven in commonmode, these transducers permit offset of imperfections associated withthe conveyance system which affect “x”-dimensional position of thesubstrate. For example, the transported thing can be made to travel avirtual straight edge in the “y”-dimension. Driven in differential mode,the transported thing can also be rotated in the “xy” plane, to correctfor orientation error also caused by mechanical imperfections of thetransport path. Note that three or more transducers can be used tosimultaneously correct for error in multiple dimensions, e.g., to“levelize” gripper or printhead height, as will be further discussedbelow.

In a split-axis system used for fabricating electronic devices on asubstrate, a “gripper” can be used to move the substrate along a firstdimension (e.g., the “y”-dimension). The gripper has a first componentthat rides along an edge or track and a second component (typically avacuum device) that engages and locks to the substrate; the transducerscan be positioned operatively between these components so as to provideselective offset between the first component and the second component attwo or more respective points of interaction, to provide both common anddifferential mode displacement as referenced above. As the firstcomponent experiences translational and rotational excursions caused bymechanical imperfections in the conveyance system (e.g., in a seconddimension), the transducers are driven so as to exactly equalize thoseexcursions in that dimension, and essentially provide for the secondcomponent a “virtual edge” or “virtual transport path” uncharacterizedby mechanical error. Note that errors can be linear or nonlinear and thecorrections correspondingly can be linear or nonlinear. In optionalembodiments, this type of system can be embodied in a printer orprinting system, e.g., with the y-dimension being a substrate transportdimension and/or one of an “in-scan” or “cross-scan” dimension, and withthe x-dimension being a printhead transport dimension and/or the otherof the “in-scan” or “cross-scan” dimension. Note that the describedreference frames are arbitrary and can be inverted or swapped for otherreference frames or for other degrees of freedom.

As noted, there may be multiple transport paths in a manufacturingsystem, and these techniques can be applied to any one of thesetransport paths or any combination of them, and can be applied tocorrect positional error in one dimension (or rotational error) orerrors in multiple dimensions. Several examples will help underscorethis point.

First, in one contemplated implementation, these techniques are used tocorrect for cross-scan dimensional error in substrate position as agripper moves along a transport path. A gripper has first and secondcomponents as referenced above and linear transducers that operativelycouple these components in at least two points of interaction, with thetransducers structured so as to provide for a “floating” pivot point. Asthe first component travels down a conveyance path, deviation from anoptical guide or from a desired optical orientation is detected; signalsproduced from this detected deviation are used to control thetransducers so as to provide “common-mode” and “differential-mode”offsets that repeatably provide for translational offset in thecross-scan dimension and rotational adjustment of the substrate, so asto drive the deviation or error to zero. The substrate therefore isadvanced in a straight path notwithstanding mechanical imperfections ofthe conveyance system. Various embodiments of the mentioned transducerswill be provided below but, briefly, in one embodiment, “voice coils”can be used for these transducers, so as to provide very precise,microscopic throws. To help provide structural support andinterconnection between the first and second components, a floating,mechanical pivot assembly compatible with the common and differentialdrive modes can also optionally be used. In other embodiments, apiezoelectric or other transducer can instead be used.

In an optional extension to this first example, gripper position (and/orthe position of the second component of the gripper) can also beregulated in an in-scan dimension. For example, in one embodiment, anelectronic drive signal (used to advance the gripper, or otherwise usedto trigger printer nozzle firing) is adjusted so as to correct forpositional error of the substrate in the in-scan dimension. It is alsopossible to use another transducer (e.g., another voice coil or othertransducer) to offset the first component relative to the secondcomponent in the in-scan dimension. In a first technique, in-scanpositional error can be measured and used to offset individual nozzlefirings (i.e., as the printhead(s) and substrate move relative to eachother, so as to effectuate nozzle firing at precisely the corrected,intended in-scan positions); for example, delays in nozzle firings canbe calculated and programmed into a printhead for each nozzle, withfirings then driven off of a common trigger signal. In a secondtechnique, a common or shared nozzle trigger signal can be generated asa function of gripper position (and/or position of the first componentof the gripper) and can be corrected for error so that the triggersignal is generated so as to simulate error-free movement of thegripper. As regards this optional extension, it was earlier mentionedthat in one implementation, correction techniques can be applied to eachof gripper and printhead conveyance paths and used in concert with aposition feedback system for each conveyance path, in order to providefor precise positioning in x and y axes and to ensure coordinate systemorthogonality and precise position control in a printing system. In onesuch implementation, the gripper system has a linear encoder thatprovides positional feedback, for example, by imaging visible marks or“ticks” associated with its conveyance path; such markings for examplecan be applied via an adhesive tape which marks “each micron” (or otherregular distance measure) of advancement relative to a track or guide.This positional feedback can optionally be used to correct for in-scandimensional advancement of the gripper (e.g., so that the gripper isinherently or transparently positioned correctly relative to the in-scandirection). In a system where such positional feedback is applied toeach conveyance path (e.g., such that a similar linear encoding systemis also used for printhead in-scan position regulation),transducer-based correction techniques can provide offsets orthogonal tothe direction of conveyance, for each of the printhead and the gripper,in order to define a coordinate reference system and to preciselycontrol droplet placement. These techniques by themselves do notnecessarily inherently correct for non-orthogonality between conveyanceaxes (e.g., x and y axes associated respectively with the gripper andprinthead conveyance systems); in some embodiments, therefore,additional techniques described herein can be optionally applied tocorrect positioning of optical beams used to mark desired transportpaths, or otherwise to control error correction systems to as to addressnon-orthogonality. When combined with optional techniques for heightregulation and/or correction, these techniques help provide for preciseposition control of all elements in the manufacturing system. Thesevarious advantages and synergies of these various techniques will beelaborated on below.

Reflecting on the principles discussed thus far, an optical source anddetector and any associated optics (depending on implementation) can beused to guide and/or sense positional deviation of a transportedcomponent. At least one transducer can be used to correct for transportpath error by displacing a thing being transported in a dimensionorthogonal to the direction of transport using both common-mode anddifferential-mode control, i.e., as a function of the detecteddeviation, using feedback. In a still more detailed embodiment, thistype of control can be applied to correct for transport path error intwo different transport paths, for example, to “y”-axis motion of afirst conveyance system and to “x”-axis motion of a second conveyancesystem, using respective sets of transducers. Correcting two differenttransport paths in this manner helps facilitate precise correction overdeposition and/or fabrication parameters. For example, in the context ofa split-axis printing system, introduced above, correction of both ofgripper/substrate path and printhead path effectively normalizes a“print grid” (a coordinate reference system used to define wheredroplets will be printed), and provides for a system where the system'sunderstanding of print grid coordinates is precisely correct and is notundermined by errors in mechanical systems associated with transport.These techniques and various combinations and permutations discussedherein (including the incorporated-by-reference documents) help providefor precise positional control over deposited droplets. For example,these techniques can be further applied to “z-axis” (e.g. height) orother dimensional motion control; alternatively, the techniquesdescribed herein can be combined with the use of per-nozzle dropletparameters and/or nozzle parameters to provide for highly accuratecontrol over deposited liquid volumes, as for example described in U.S.Pat. No. 9,352,561 and U.S. Patent Publication No. 2015/0298153.

This disclosure will roughly be organized as follows: (1) FIGS. 1-3Ewill be used to provide an introduction relating to depositing amaterial on a substrate, causes of fine alignment error and associatedremedies; (2) FIGS. 4A-5 will be used to introduce more specifictechniques, that is, relating to on-line and off-line processes relatingto measuring/detecting and counteracting error in a contemplatedsplit-axis print environment; (3) FIGS. 6A-6E will be used to describespecific mechanical structures in one or more detailed embodiments; (4)FIGS. 7A-H will be used to discuss various use cases and optionalextensions; and (5) FIGS. 8A and 8B will be used to discussmultidimensional control (e.g., x and z axis control) of a conveyancesystem component.

Prior to proceeding to the introduction, it would be helpful to firstintroduce certain terms used herein.

Specifically contemplated implementations can include an apparatuscomprising instructions stored on non-transitory machine-readable media.Such instructional logic can be written or designed in a manner that hascertain structure (architectural features) such that, when theinstructions are ultimately executed, they cause the one or more generalpurpose machines (e.g., a processor, computer or other machine) each tobehave as a special purpose machine, having structure that necessarilyperforms described tasks on input operands in dependence on theinstructions to take specific actions or otherwise produce specificoutputs. “Non-transitory” machine-readable or processor-accessible“media” or “storage” as used herein means any tangible (i.e., physical)storage medium, irrespective of the technology used to store data onthat medium, e.g., including without limitation, random access memory,hard disk memory, optical memory, a floppy disk, a CD, a solid statedrive (SSD), server storage, volatile memory, non-volatile memory, andother tangible mechanisms where instructions may subsequently beretrieved by a machine. The media or storage can be in standalone form(e.g., a program disk or solid state device) or embodied as part of alarger mechanism, for example, a laptop computer, portable device,server, network, printer, or other set of one or more devices. Theinstructions can be implemented in different formats, for example, asmetadata that when called is effective to invoke a certain action, asJava code or scripting, as code written in a specific programminglanguage (e.g., as C++ code), as a processor-specific instruction set,or in some other form; the instructions can also be executed by the sameprocessor or different processors or processor cores, depending onembodiment. Throughout this disclosure, various processes will bedescribed, any of which can generally be implemented as instructionsstored on non-transitory machine-readable media, and any of which can beused to fabricate products. Depending on product design, such productscan be fabricated to be in saleable form, or as a preparatory step forother printing, curing, manufacturing or other processing steps, thatwill ultimately create finished products for sale, distribution,exportation or importation where those products incorporate aspecially-fabricated layer. Also depending on implementation, theinstructions can be executed by a single computer and, in other cases,can be stored and/or executed on a distributed basis, e.g., using one ormore servers, web clients, or application-specific devices. Eachfunction mentioned in reference to the various FIGS. herein can beimplemented as part of a combined program or as a standalone module,either stored together on a single media expression (e.g., single floppydisk) or on multiple, separate storage devices. The same is also truefor error correction information generated according to the processesdescribed herein, i.e., a template representing positional error as afunction of transport path position can be stored on non-transitorymachine-readable media for temporary or permanent use, either on thesame machine or for use on one or more other machines; for example, suchdata can be generated using a first machine, and then stored fortransfer to a printer or manufacturing device, e.g., for download viathe internet (or another network) or for manual transport (e.g., via atransport media such as a DVD or SSD) for use on another machine. A“raster” or “scan path” as used herein refers to a progression of motionof a printhead or camera relative to a substrate, i.e., it need not belinear or continuous in all embodiments. “Hardening,” “solidifying,”“processing” and/or “rendering” of a layer as that term is used hereinrefers to processes applied to deposited ink to convert that ink from afluid form to a permanent structure of the thing being made; these termsare relative terms, e.g., the term “hardened” does not necessarilyrequired that the finished layer be objectively “hard” as long as thefinished form is “harder” than the liquid ink deposited by the printer.The term “permanent,” as in a “permanent layer,” refers to somethingintended for indefinite use (e.g., as contrasted with a manufacturingmask layer which is typically removed as part of the manufacturingprocess). Throughout this disclosure, various processes will bedescribed, any of which can generally be implemented as instructionallogic (e.g., as instructions stored on non-transitory machine-readablemedia or other software logic), as hardware logic, or as a combinationof these things, depending on embodiment or specific design. “Module” asused herein refers to a structure dedicated to a specific function; forexample, a “first module” to perform a first specific function and a“second module” to perform a second specific function, when used in thecontext of instructions (e.g., computer code) refer tomutually-exclusive code sets. When used in the context of mechanical orelectromechanical structures (e.g., an “encryption module,” the term“module” refers to a dedicated set of components which might includehardware and/or software). In all cases, the term “module” is used torefer to a specific structure for performing a function or operationthat would be understood by one of ordinary skill in the art to whichthe subject matter pertains as a conventional structure used in thespecific art (e.g., a software module or hardware module), and not as ageneric placeholder or “means” for “any structure whatsoever” (e.g., “ateam of oxen”) for performing a recited function. “Electronic” when usedto refer to a method of communication can also include audible, opticalor other communication functions, e.g., in one embodiment, electronictransmission can encompass optical transmission of information (e.g.,via an imaged, 2D bar code), which is digitized by a camera or sensorarray, converted to an electronic digital signal, and then exchangedelectronically. The terms “transducer” and/or “actuator” are usedgenerally in an interchangeable manner, and without regard to the formator type of transducer or actuator; for example, a “voice coil” and a“piezoelectric transducer” are each examples of actuators/transducers.

Also, reference is made herein to a detection mechanism and to alignmentmarks or fiducials that are recognized on each substrate or as part of aprinter platen or transport path or as part of a printhead. In manyembodiments, the detection mechanism is an optical detection mechanismthat uses a sensor array (e.g., a camera) to detect recognizable shapesor patterns on a substrate (and/or on a physical structure within theprinter). Other embodiments are not predicated on a sensor array, forexample, a line sensor can be used to sense fiducials as a substrate isloaded into or advanced within the printer. Note that some embodimentsrely on dedicated patterns (e.g., special alignment marks) while othersrely on recognizable optical features (including geometry of anypreviously deposited layers on a substrate or physical features in aprinter or printhead), each of these being a “fiducial.” When referringgenerally to “light,” “optics” or “optical,” in addition to usingvisible light, alternative embodiments can rely on ultraviolet or othernonvisible light, magnetic, radio frequency or other forms ofelectromagnetic radiation. Also note that some embodiments herein willbe discussed with reference to a printhead, printheads or a printheadassembly, but it should be understood that the printing systemsdescribed herein can generally be used with one or more printheads; inone contemplated application, for example, an industrial printerfeatures three printhead assemblies, each assembly having three separateprintheads with mechanical mounting systems that permit positionaland/or rotational adjustment, such that constituent printheads (e.g., ofa printhead assembly) and/or printhead assemblies can be individuallyaligned with precision to a desired grid system. Various other termswill be defined below, or used in a manner in a manner apparent fromcontext.

I. Introduction

FIGS. 1, 2A-2B and 3A-3E are used to introduce several techniquesdiscussed in this disclosure and some of the problems these techniquesaddress.

More specifically, FIG. 1 represents a prior art process 101 associatedwith some type of transport mechanism. In this specific example, it isassumed that there is a substrate 103 that is to be printed upon withdroplets deposited at selected nodes of a print grid 105; the print grid105 is illustrated as centered in the substrate to denote that in thisposition, it is indented that droplets of ink from the printhead willland at precise positions (i.e., at locations represented by nodes ofthe print grid) with predictability that translates to layer uniformity.Note however, that the print grid, while illustrated in this manner, isdefined relative to the printer (not specifically the substrate) andextends to anywhere that printing can occur (e.g., the printable areacan be larger than the substrate, and error in substrate position canpotentially translate to error in droplet landing locations). Also, thespacings of vertical lines and horizontal lines are generally thought tobe predictably spaced, however, this is typically based on an assumptionthat advancement along x and y transport paths are precisely accurate(and/or linear). Finally, note also that while a printer, substrate andprint grid are exemplified here, these problems are not unique toprinters and that techniques described herein can be applied to a widevariety of situations where something is to be mechanically transported,rotated or moved. The context of a printing process, a substrate and aprint grid are to be used as a non-limiting, illustrative example tointroduce problems and techniques described in this disclosure.

It is assumed that printing will occur as the substrate is generallytransported as represented by arrows 104 and, further, that a conveyancesystem mechanism is to guide the substrate along a transport path 107;this transport path is illustrated in FIG. 1 as slightly crooked,representing in this example mechanical imperfections in the conveyancesystem (e.g., in some type of edge guide, track or traveler, or othermeans used to steer the substrate 103). Note that in a typicalindustrial printing process, such as for making OLED display panels asdescribed earlier, the substrate might be on the order of two meters bythree meters in size, whereas the nonlinearities in path 107 might be onthe order of microns or even smaller. The crookedness (or other error)in path 107 as depicted in FIG. 1 is thus exaggerated for purposes ofdiscussion and illustration. Whereas error of this scale might beinconsequential in many applications, in certain manufacturing processes(e.g., the manufacture of OLED displays and/or certain other electronicdevices on large substrates), this type of error might limit achievableproduct size, lifetime, or quality. That is to say, the dropletsgenerally speaking have to be deposited at precise positions so thatthey meld together and produce a homogeneous layer without leaving gapsor pinholes; the droplets upon landing spread only to a limited extent,and surface irregularity in the finished layer can limit achievablelayer thinness and otherwise create quality issues. Even slightmisposition of droplet landing locations can affect product qualityand/or manufacturing reliability.

FIG. 1 as a figure is conceptually divided into two halves, including aleft half and a right half. The left half of the figure shows thesubstrate 103 and a slightly crooked transport path 107. The substrate103 is to be advanced back and forth along this path 107 in what isgenerally designated the “y” dimension, as referenced by arrows 104.Numeral 103 denotes that the substrate is at some point properly alignedwith the print grid 105; the print grid as depicted in this FIG. is anabstraction where vertical lines represent the apparent paths ofrespective nozzles of a printhead as the printhead and substrate aremoved relative to each other, while horizontal lines denote a digitalfiring signal or other ability of a nozzle to be recharged and firerepeated droplets of ink, i.e., the spacings of these horizontal linestypically represent “how fast” the nozzles can be fired. Perhapsotherwise stated, the print grid 105 has nodes, each of which representsan opportunity to eject a droplet of ink; as indicated earlier, it isdesired to deposit ink in a manner that is precisely controlled as toposition, and leaves no pinholes, which is in part achieved as afunction of having precise knowledge as to where each droplet will landon the substrate. Note further that droplets are deposited at discretepositions, but are viscous and thus typically spread to form acontinuous liquid coat having no gaps or irregularities; volume per unitarea is generally correlated in advance with a desired thickness orother property of the final layer, and thus droplet densities andrelative positions can in theory be selected in a manner (given expecteddroplet size) to produce the desired effect, e.g., to promote an evenlayer of desired thickness following spreading and melding of droplets(this is discussed in U.S. Pat. No. 8,995,022, which is incorporated byreference).

The print grid 105 is graphically depicted at the left-half of the FIG.in a manner “squared up” with the substrate 103, denoting that printingwill general occur at desired droplet landing locations.

Unfortunately, the errors in the transport path 107 (i.e., thecrookedness) can effectively distort the print grid 105, meaning thatdroplets do not necessarily land where they are supposed to relative tothe substrate, because the substrate as it is advanced experiences finepositional and rotational error. The right hand side of FIG. 1 showssubstrate translation and/or orientation error as the substrate isadvanced from a first position do along the transport path 107, with thesubstrate position and yaw denoted by 103′ relative to a (virtual) ideal“reference edge” 109, to a second position d₁ along the transport path,with the substrate position and yaw denoted by 103″ relative to thereference edge 109. As seen, the substrate experiences, due to theerrors (e.g., crookedness) in the transport path 107, offset androtational error in multiple dimensions; the error in this example isseen to be horizontal and vertical offset Δx₀ and Δy₀, and angularoffset Δθ₀ within the xy plane when the substrate has been moved to thefirst position d₀, and different horizontal and vertical offset Δx₁ andΔy₁, and angular offset Δθ₁ when the substrate has been advanced to thesecond transport path position d₁. Because the nature of these errorschanges as the substrate is advanced, these errors distort the printgrid, meaning that although a planned print process should (in theory)produce the desired layer properties, in fact, droplet deposition can bedistorted, potentially creating quality issues. If left uncorrected,these various errors may create pinholes, thin zones and otherimperfections and that limit the precision and/or quality achievablewith the printing systems; once again, this may limit device size (e.g.,it may be difficult to impossible to produce high quality miniaturizedproducts or products that have better quality or resolution, such asvery thin large area display screens). The effect of error of the typementioned is to distort the print grid; for example, while the systemand print planning might effectively assume a rectilinear print grid(105 in FIG. 1), “y”-error and/or jitter (i.e., parallel to thetransport path) effectively distorts the separation between thehorizontal lines of that print grid; similarly, “x”-dimension errorand/or jitter effectively distort separation between the vertical linesof that print grid, with the consequence being error in depositionlocations of the individual droplets. These types of errors might resultin too little or too great fluid deposition in various pixel wells, orother non-uniformities, potentially leading to brightness and/or huevariation or other errors in a finished display—in the context of a“macroscopic layer” such as an encapsulation error that spans manyelectronic components, these types of errors can lead to layernon-uniformity and potentially compromise layer function.

Note that as illustrated in this example, the depicted errors in somecases may be simply a repeatable function of the transport path 107,i.e., because the transport path in this example is seen as curved,there is non-linear displacement in the x-dimension, non-lineardisplacement in the y-dimension, and nonlinear skew; other types oferrors, such as z-dimensional error, pitch and roll, can alsopotentially occur on a repeatable basis but are not depicted in thisparticular FIG. Thus, in an application such as an industrial printerused to create fine (e.g., micron or smaller scale) electronic, optical,or other structures that rely on uniformity of the type mentioned, andwhere a series of substrates is to be printed on as part of an“assembly-line” style fabrication process, the same errors canpotentially occur from substrate-to-substrate. There are also otherpotential sources of error which may be unique to a given substrateand/or which might represent changing conditions, for example,temperature variation.

While error affecting substrate travel has been illustrated, there arealso potentially other sources of similar error that can affect devicequality and/or process reliability. For example, a split-axis printertypically moves not only the substrate, but a printhead or camera, orother mechanical components. Briefly, in systems that move one or moreprintheads (generally in the “x” dimensions relative to FIG. 1), similarpath error can result in “x,” “y” rotational or other error in theprinthead(s) (relative to the dimensions of FIG. 1). For example, if aprinthead has error at different positions, such typically also has theeffect of distorting the vertical lines of the print grid 105 (i.e.,making them unevenly spaced). Similar analogies can be stated for othertransport path analogies in an industrial printing system of the typereferenced. It is generally desired to reduce the effects of theselayers to improve predictability and reliability in layer fabricationand, generally, to have the ability to fabricate thinner, homogeneouslayers.

To address these issues, one embodiment provides a transport pathcorrection system that detects and negates one or more forms of patherror. FIG. 2A shows an embodiment 201 that has two principalcomponents, including a first, track-guided component 203 and a second,offsettable component 205. Both of these components are to movegenerally together in the general direction represented by arrows 206.In one implementation, these two components can be part of a vacuumgripper that is used to engage and advance a substrate along a “fast”axis; in another implementation, these two components can instead bepart of a printhead traveler, for example, that travels a track and thatmounts a printhead for use in printing droplets onto a substrate.

The depicted embodiment uses an optical source 207, which directs a beamof light 202 in a manner that will serve to guide or facilitate desiredtravel, in this case, perfectly straight travel that simulates a“virtual edge guide.” In the depicted scheme, the optical source 207 isstationary and the beam 202 it emits is sensed by two optical detectors208 and 209, both mounted to the second component. In addition, two beamsplitters 211 and 212 are used to redirect light from the optical pathto the detectors 208/209 in a manner that will be used to sensedeviation of the second component from the optical path and to correctfor that deviation. Note that the depicted structure is not required forall embodiments, e.g., specifically-contemplated variations feature thelight source mounted to the second component with one or morebeam-splitters and/or one or more detectors being stationary; otherconfigurations are also possible and will occur to those having ordinaryskill in the art.

To correct for path deviations, a signal from each of the detectors isfed to processing circuitry 214/215 as necessary, which applies afunction “F” to those signals in order to develop correction signalsthat will be applied as feedback to correct for path deviation; whiletwo sets of such circuitry are depicted, it is possible to use only onecircuit (e.g., a software-driven processor) or to have significantoverlap of circuit elements. The correction signals, in turn, are fed toone or more transducers “T” which immediately apply correction so as to“zero-out” deviation from the optical path; that is, advantageously, theprocessing circuitry and/or detectors produce signals which are “zero”(or do not cause further transducer adjustment) when the secondcomponent 205 is synched with the optical path and which always drive areturn to zero when there is deviation from the optical path; note thatthis structure is not required for all embodiments. In the figure, thedepicted embodiment is seen to rely on two transducers, specificallynumbered 216 and 217; each of these transducers provides for asubstantially linear throw in a direction orthogonal to the direction oftransport. In this example the use of two transducers at respectivepoints of interaction (c1/c2) between components 203 and 205 provide forcommon-mode and differential-mode control, to respectively offsetcomponent 205 linearly from the first component 203 (in the direction ofarrows 213) and to provide for rotation of component 205 relative tocomponent 203, as represented by the angular measure “0.” Thetransducers can be any desired type of transducer suitable to the throwsat-issue, including without limitation, piezoelectric transducers; in anembodiment where a substrate is supported by an air bearing (and thecomponent 205 uses a vacuum gripper to engage the substrate), thetransducers can advantageously be voice coils, which provide forrelatively large maximum throws (e.g., from submicron to 100 microns ormore) with a high degree of repeatability and reliability. Thecombination of common-mode and differential mode control over thetransducers essentially provides for a floating pivot point betweencomponents 203 and 205 which can be offset generally in the “x”direction (note that the xyz coordinate labels seen in the figure arearbitrary in this example). To help provide mechanical structuralsupport between components 203 and 205, in some embodiments, amechanical linkage (“M”) 218 can be used which constrains components 203and 205 to move with each other in the “y” direction while at the sametime permitting free offset between these components in the “x”direction and relative xy rotation. Such additional structural linkagecan be especially advantageous where voice coils are used as thetransducers, to help constrain any unnecessary loading on thetransducers in directions orthogonal to a direction of transducerdisplacement. Numeral 221 provides additional detail relating to adetector, and shows a two cell design, with the cells being denoted byvalues “a” and “b;” briefly, in one design, light from the light sourcehits one or both of these sensors, and a difference between voltagesproduced by each of these sensors is used to straighten the secondcomponent 205 relative to the optical path. For example, in a two-celldesign, the value “(a−b)/(a+b)” produces a positive or negative outputin proportion to the amount of deviation from the midpoint of the twocells; such a signal alone can be used to drive the associatedtransducer to a position where the optical path is centered between thetwo cells. Note that in some embodiments, processing circuitry 214/215can be combined with the detectors, e.g., purchased as a single unitthat provides a digital or analog output representing disproportionalsignal sensed by each cell of the detector.

In some embodiments, it is possible to sense path deviation in more thanone dimension, e.g., in each of x and z dimensions in connection withthe depicted coordinate system. For detection of this deviation, afour-cell design can be used, represented by numeral 223 in the figure.For example, the value “[(a+c)−(b+d)]/(a+b+c+d)]” can be used to sense xdimensional deviation from the desired path, and the value[(a+b)−(c+d)]/(a+b+c+d)] ca be used to sense z dimensional deviationfrom the desired path. Note that a separate, second set of correctiontransducers (not seen in this figure) may be required, depending onimplementation, to correct for errant motion in a second (or third,fourth, etc.) degree of freedom; the configuration of transducers issimilar to that depicted already in FIG. 2A, except that the directionof transducers displacement can be, e.g., along the z dimension. Noteboth that the use of linear transducers is not required for allembodiments and, conversely, corrections can be made for one or morerotational degrees of freedom, for example, to levelize a surface oredge and correct for pitch, yaw and/or roll.

FIG. 2A also illustrates a few further optional components that may beused in some embodiments. First, numeral 225 refers to an adjustmentmechanism that can be used to align and/or adjust the optical source207. In one embodiment, the optical source is a laser and numeral 225references a screw-based precision mount that changes the attitudeand/or yaw of the laser relative to the direction of transport. Second,numerals 227/229 refer to a beam splitter and detector that can be usedfor the same purpose, e.g., by mounting such a detector in a manner thatis fixed relative to the optical source 207, the optical source can beperiodically recalibrated (and adjusted, e.g., using adjustmentmechanism 225) to ensure proper orientation. It is also possible to usea standard 231 at a far end of the optical path to assist with alignmentand/or automatically provide feedback relating to proper orientation ofthe light source; in one embodiment, this standard can be a simpletarget or crosshairs (e.g., a laser is adjusted until its beam strikescenter) and in another embodiment, this standard can be adetector/circuit that provides electronic feedback, e.g., permittingmanual or automatic alignment of the light source.

FIG. 2B is a flow chart that depicts method steps 251 that implementsome of the techniques introduced above. As denoted by numeral 252, themethod can be embodied in a manufacturing system having a transport pathwhere it is desired to correct for fine motion, position or orientationerror of a conveyance system; for example, a manufacturing system canperform high precision product “assembly-line-style” manufacturing usinga printer for materials deposition, as introduced previously. Initially,alignment or calibration steps 253 can be performed to ensure that anoptical beam is directed exactly as desired to mark straight travel; forexample, as introduced previously, the optical beam can be used to imagea stationary target with crosshairs and adjusted 254, either manually bya human operator or automatically based on electronic feedback, untilthe optical beam is incident with a reticle formed by the crosshairs. Ina typical implementation, calibration can be performed at initialinstallation, at start-up, periodically (e.g., daily or weekly), at theoccurrence of certain milestone events (e.g., detected error greaterthan a threshold, or temperature change greater than a thresholdamount), or otherwise as desired. A series of substrates 255 is thensequentially introduced and aligned with the printer's coordinatereference system to ensure that individual panel products on thosesubstrates are in a known position relative to the optical beam (e.g.,as formed by a properly aligned laser); this process will be furtherdiscussed below, but in one embodiment, the combination of opticalalignment marks for each transport path (e.g., position feedback for thegripper and printhead) and the use of two transducer-based error offsetsystems and associated optical paths effectively define a coordinatereference system for the printer and regulate motion in that coordinatereference system; each given substrate in the series can be individuallyaligned to this coordinate reference system by imaging fiducials on thegiven substrate and adjusting either the substrate position/orientationor the print recipe so that printing will occur on each panel exactly asdesired. Printing then occurs on the aligned substrate; as eachconveyance or transport system is operated, error (i.e., deviation fromeach marked optical path) is dynamically measured, per numeral 255,optionally for more than one transport path and/or one dimension pertransport path, as indicated by numeral 257, and optionally using oneerror correction system to correct for multidimensional error (e.g., xand z deviation using a 4-cell detector design), per numeral 258.Dynamic corrections 259 are then applied as feedback to instantaneouslycorrect error and to change the position and orientation of the “secondcomponent” relative to the first component, so as to drive deviationfrom the associated optical path to zero, i.e., such that thetransported “thing” (e.g., substrate, camera, printhead or otherelement) travels the desired, perfectly straight path notwithstandingmicroscopic jitter that can still influence the conveyance system. Asnoted earlier, in one embodiment, position regulation along thedirection of conveyance (e.g., in a direction parallel to an opticalbeam used as a guide) can be optionally assisted through the use of aposition regulation system, for example, which measures marks on anadhesive tape proximate to the conveyance path, e.g., with alignmentmarks for every micron of travel along the transport path; thetransducer-based correction system in such an embodiment is thereforerelied upon to correct for path deviation which in a directionorthogonal to the direction of the marked optical path, as well asrotational deviation (e.g., optionally using two or more transducers,per numeral 265, and differential-mode control over the two or moretransducers, per numeral 267). The result is that the thing beingtransported follows a virtual, ideal path, as referenced earlier and asidentified by numeral 269.

Having introduced transducer-based correction and the use of an opticalguide, applications to path error control will now be discussed, againin the exemplary context of an industrial split-axis printerenvironment.

FIG. 3A shows an embodiment 301 for reducing conveyance path error in agripper system that advances a substrate, such as the substrate 103 fromFIG. 1. More specifically, it is once again assumed that the substrateis to be advanced back and forth along a path represented by arrows 104.In this example, the substrate will be advanced using a gripper; a firstcomponent 302 of the gripper will travel along path 107 (from FIG. 1),generally along a track extending in the “y”-dimension. The gripper alsohas two transducers (T), 305 and 306, which operatively connect thefirst component 302 with a second component 303, which engages an edgeof the substrate. In one exemplary case, the substrate is supported onan air bearing above a floatation table to provide for nearlyfrictionless support; in other examples, other mechanisms can be usedfor support and transport. The two transducers each are controlled todisplace the second component relative to the first component along acommon direction (e.g., in an “x” dimension as illustrated in the FIG.),as represented by arrows 310. Each transducer can be independentlycontrolled, leading to a situation where “common-mode” control offsetsthe second component linearly toward and away from the first component302 in the x-dimension at the respective point of engagement, while“differential-mode” control pivots second component relative to thefirst about a pivot point “X_(pvt).” Because the transducers can beelectronically driven in a manner having both common and differentialdrive components, the pivot point “X_(pvt)” is seen to be a floatingpivot point; in some embodiments, this floating pivot point can be anabstract concept, while in others, a mechanical structure provides forpivot while also providing a structural coupling between the gripper'stwo components. Note that while this figure shows the gripper asengaging the substrate near its top-left corner, in a typicalenvironment, it may be desired that the gripper engage the substratemidway along its length, e.g., to provide reciprocal moments for thetransducers (e.g., to facilitate control over both common-mode anddifferential-mode displacement).

The first component 302 follows the error-encumbered path, 107 from FIG.1, while the second component locks to the thing being transported(e.g., in this case, the substrate 103, e.g., using a vacuum) and isdynamically offset so as to follow a straight path. The transducers 305and 306 are seen to be independently controllable to move the substrateas indicated by arrows 308 and 309, and are controlled in a manner so asto exactly negate x-dimension- and θ-rotation-induced error in the path107, such that substrate motion tracks an ideal “reference edge” (seeline 109 from FIG. 1). Note that in alternative designs, instead ofhaving linear throws that are parallel to one another, transducer 305could effectuate rotation while transducer 306 could effectuate a linearthrow, or the transducers could be made to produce offsets in the “y”dimension or any other desired dimension, with corresponding effect ofmitigating substrate position or rotation error. In FIG. 3A, thegripper's first component 302 moves along the “y” dimension, while thetransducers 305 and 306 each push and pull the substrate along a linearrange of motion along the “x” dimension, via contact at respect contactpoints “c.” Again, each transducer in this example can be a linearmotor, a piezoelectric transducer, a voice coil, or another type oftransducer.

In the split-axis printing system of this example, the substrate isadvanced in the “y” dimension relative to the printhead(s) for aparticular “scan” or raster motion; the “y” dimension in this exampletherefore also forms the “in-scan” dimension. The printhead(s) are thenmoved in the “x” dimension to reposition the printhead(s) for an ensuingscan (i.e., in the “cross-scan” dimension); the substrate is thenadvanced in the reverse direction, for the ensuing scan, with successivescans continuing until the entire liquid coat has been created. Thesubstrate can then be advanced (typically out of the printer, to anotherchamber), where the liquid coat is cured, dried or otherwise processedso as to convert the liquid coat to a permanent structure having desiredelectrical, optical and/or mechanical properties. The printing system isthen ready to receive another substrate, for example, to perform similarprinting on that ensuing substrate according to a common, predefined“recipe.”

It was noted earlier that error along transport path 107 (from FIG. 1)can potentially lead to error in multiple dimensions, i.e., not justoffset in the x dimension. With a conveyance system regulated forposition (e.g., using alignment marks as referenced earlier), this canbe less of a concern, but in other systems, variations in angle of thatpath might lead to nonlinearities in y-position of the substrate aswell. In such an implementation, y-dimensional error can optionally becorrected using other forms of means 311 for correcting substrate motionin the “in-scan” dimension; options include for example, using a thirdtransducer 314 to effectuate throws of the gripper's first and/or secondcomponents in the in-scan dimension, to normalize y-dimensionaladvancement of the substrate. In other embodiments, feedback can insteadbe used to adjust an electronic control signal 315 (e.g., as a feedbacksignal, delta signal, or electronic drive signal) for advancement of thegripper, to impart a slight velocity increase or decrease (Δv) tocounteract y-dimensional error, or the gripper's motion can be caused tomatch positional markers as introduced above. In yet another optionalembodiment, it is also possible to perform adjustments in software, forexample, computing and programming individual, y-position dependentnozzle firing delays (as represented by box 316), i.e., the nozzles ofthe printhead can, in some embodiments, be “told” to print slightlyearlier or later as the substrate and printhead(s) are moved relative toeach other in the “y” dimension, in a manner that exactly cancels out“y” dimension positional error of the substrate relative to the printer.Also, per numeral 317, in another embodiment, it is possible to adjust a“trigger” signal used to time nozzle firing, to have the effect ofshifting the horizontal lines of the print grid (see numeral 105 fromFIG. 1) so as to cancel out positional error of the substrate relativeto the printer. Note that “in-scan” or “y-axis” compensation of agripper is not required for all embodiments.

FIG. 3A also shows an optical system used to define desired travel; asintroduced earlier, an optical beam 318 is directed from a light source319 (e.g., a laser) in the direction of travel (e.g., in this case,parallel to the y-dimension as referenced in the figure. At least onesensor or detector 320 is used to image this path and detect deviationfrom the optical beam 318 as the gripper and substrate move along theirtransport path. Advantageously, the at least one sensor or detector 320is mounted in a manner fixed to the gripper's second component 303, suchthat as travel occurs, feedback signals derived from the sensor ordetector 320 are used to reorient and displace the substrate in the xdimension and in xy orientation so that substrate motion exactlycorresponds to the marked optical path (318), notwithstanding thatmotion of the gripper's first component continues to experiencemechanical jitter. As noted earlier, in contemplated variations, theoptical source 319 and sensor(s)/detector(s) 320 can be configureddifferently, for example, with the optical source 319 mounted to thegripper's second component 303, using beam splitter optics mounted tothe gripper, and so forth; such design variations are well within theskill of one familiar with optics.

Reflecting on the subject matter of FIG. 3A, it should be observed thatby using two or more transducers in a mechanical conveyance system, onecan correct for errors in the transport path or other motion errors(e.g., for a non-linear guide or track or edge). Whereas path errorsmight exist as represented by numeral 107 in FIG. 1, the techniques andstructures introduced above attempt to “live with” this repeatable errorin the transport path (e.g., the gripper's first component 302 continuesto travel this error-encumbered path), but the transducers effectuatethrows or other corrections to equalize and/or negate this path error inat least one dimension, and thus the thing being moved (the substrate inthis example) travels an idealized path, such as represented by numeral109 in FIG. 1. In one embodiment, these motion corrections can bemechanically effectuated by two or more transducers, each having alinear throw parallel to one another and substantially orthogonal to adirection of conveyance (e.g., transducers 305 and 306, eachindependently controllable with a linear throw in a direction (e.g.,310) substantially orthogonal to a direction of arrows 104).

While these techniques can be applied to virtually any mechanicalconveyance system, it was earlier-mentioned that one field that couldbenefit from these techniques relates to industrial printers where inkdroplets have to be deposited at very precise positions. For example,one contemplated embodiment is as a printer used to fabricate lightemitting devices, such as organic LED display devices (e.g., cell phonescreens, HDTV screens, and other types of displays), and “panel” devicessuch as solar panels. In this regard, in the application discussed above(e.g., where a substrate meters wide and long is printed upon), a numberof conventional systems rely on an air flotation table to advance thesubstrate during printing. The gas ingress and egress in such a systemcan be carefully controlled, to avoid imparting effects to the substrate(e.g., temperature, electrostatic charge buildup or other effects whichmight influence ink behavior) that could potentially produce defects inthe finished layer. In other words, gas flow is used to create a fluidicbearing underneath the substrate, to create a substantially frictionlesssurface that the substrate is moved on during printing; the secondcomponent 303 from FIG. 3A in such an application can support a vacuumchuck that engages the substrate, or multiple vacuum locks that engagerespective parts of the substrate. In such an application, in order toachieve the “micron-scale” (or smaller) throws used to negatenon-linearities and provide for preside path advancement, thetransducers 305 and 306 can advantageously be formed as voice coilswhich use compression and expansion (i.e., in a direction normal to adirection of force supported by the gas bearing of the floatation table)to effectuate the microscopic throws used to achieve precise printheadand nozzle alignment with the substrate. That is to say, for electronicflat panel fabrication in particular, and for OLED display devicefabrication in particular, it has been found that (frictionless)flotation support and the use of a vacuum gripper is important tominimizing defects and maximizing device lifetime, and the use of voicecoils as the transducers provide an effective component for providingthe required throws in such a system. Other types of transducers,however, can also be used to achieve throws pertinent to the particulartype of application, for example, through the use of piezoelectrictransducers, linear motors or other types of transducers. In such asystem, a floating, mechanical pivot mechanism can optionally be used inaid of the voice coils to provide structural linkage and mechanicalsupport for error correction.

FIG. 3B provides a view 321 similar to the view of FIG. 1, but furtherillustrates ends attainable using the mechanism of FIG. 3A. Morespecifically, FIG. 3B shows the substrate 103 and gripper from FIG. 3Aas they advance along the path 107. As with FIG. 1, the path 107 is onceagain assumed to have error manifested as some form of crookedness orvariation; once again, this could be error in an edge guide, track orother mechanism—this error imparts positional and/or rotational error tothe gripper. In this case, however, the gripper is seen as havingtransducers “T” which are controlled so as to counteract this error,e.g., in the form of voice coil displacements that compensate for orthat equalize variations in the path 107. Note again that the magnitudeof error is seen as greatly exaggerated relative to the scale of FIG.3B, e.g., in practice, the path may be meters long (e.g., for a 3 meterlong substrate is transported through a room-sized printer), while thecrookedness may be on the order of micron or submicron in scale.

At position d₀ of the gripper along the path, it will be recalled fromFIG. 1 that native transport path error was equivalent to Δx₀, Δy₀, andΔθ₀. For the system of FIG. 3B, however, the transducers are actuated todisplace and/or rotate the substrate, as seen at the lower right handside of FIG. 3B and as designated by numeral 103′. That is, thetransducers “T” displace the gripper's second component and thesubstrate relative to the gripper's first component and the track oredge guide 107 so as to have absolute position x₃, y₃ and θ₃. In thecontext of FIG. 3B, the quantity x₃ represents an absolute x-positionthat effectively defines a virtual edge 323 offset from theerror-encumbered transport path 107, the quantity y₃ corresponds tooptional positioning offset of the substrate to offset it to anarbitrary “smoothed” or normalized advancement (330) relative to thein-scan (or transport) direction, and the quantity θ₃ corresponds to adesired angular orientation of the substrate; for the example of FIG.3B, it can be assumed for the moment that y₃ and θ₃ are “zero,” e.g.,that the substrate is oriented so as to be exactly vertical (i.e.,squared off relative to the flotation support table, without“y”-dimensional correction, though this need not be the case for allembodiments). In FIG. 3B, the print grid is depicted at numeral 105′ tohave a consistent x and θ relationship relative to the substrate 103′;as the substrate is advanced from position do to position d₁, thetransducers are controlled so as to maintain this consistent positionalrelationship between the substrate and the vertical lines of the printgrid, i.e., such that the substrate is aligned (notwithstanding erroralong the path 107) to have absolute position x₃ and θ₃, and is thusdepicted at 103″ as having exactly this relationship relative to theprint grid at 105″. Note that in these examples, although the print gridis illustrated as maintaining a predetermined relationship relative tothe substrate, the print grid is defined by the printhead positioningand substrate and printhead conveyance systems, and what is reallydesired is that the printhead and substrate conveyance mechanismmaintain a consistent, predetermined relationship relative to eachother, and that a coordinate system established by this linkage beprecisely aligned relative to each product being fabricated; in someembodiments, a printer coordinate reference system is first calibrated(and regulated), so as to effectively define the print grid, and eachthe substrate (or a product being fabricated thereon) is thereafterspecially aligned relative to the print grid as it is introduced (i.e.,to the printer), via a per-product or per-substrate alignmentprocess—this will be further exemplified below.

Equations are depicted at various positions in the FIG. to indicate howa constant positional relationship is maintained. More specifically, itwill be recalled that native, repeatable error in the transport path 107at position do equated to positional and rotational offsets of Δx₀, Δy₀,and Δθ₀. The transducers “T” are therefore controlled so as to addfurther offsets of Δx₂, Δy₂, and Δθ₂, where these values are applied asa function of detected error at position do along the transport path.That is, in one embodiment, these values are the negative of the errorΔx_(θ), Δy_(θ), and Δθ₀, i.e., they exactly cancel the error andoptionally offset the substrate to some predetermined x/y/θ value. Inone embodiment, the depicted transducers “T” only correct the substrateposition in x and θ (e.g., any “y” dimensional correction is optionallyeffectuated using a position feedback/regulation system, such aspreviously described). Note how, at position d₁, the transducers arecontrolled so as to add different offset as a function of differenterror at position on the transport path 107, i.e., to add offsets ofΔx₄, Δy₄, and Δθ₄. As depicted in FIG. 3B, values x₅ and θ₅ can beexactly equal to values x₃ and θ₃, though once again, this need not bethe case for all embodiments.

Positional control at micron scale or better in many respects is lessintuitive than it might seem, e.g., in one embodiment, each of thegripper conveyance system and the printhead conveyance system mounts acamera, which is used to find a common alignment mark and therebyestablish a origin for a coordinate system matching the two transportpaths. This process, and the conveyance systems for each of theprinthead(s) and substrate in such a system, effectively define theprinter's coordinate reference system (and in large part determineconfiguration of a print grid according to which droplets can bedeposited). U.S. Provisional Patent Application No. 62/459,402,incorporated earlier by reference, provides information relating to theuse of these cameras, position detection, and related calibration;basically stated, in addition to finding a common coordinate (or“origin”) point in one disclosed system, each conveyance system uses anoptical tape and optical sensor to provide precise (e.g.,micron-by-micron) position detection and feedback, such that theconveyance system (e.g., first component of the gripper) “knows” exactlywhere it is relative to the printer's coordinate system, and thesevarious components cooperate to effectively define a complete printercoordinate system; indeed, the use of such a system can obviate the needfor component offset in the direction of transport, e.g., the gripper issimply driven to the specific, appropriate position value in thedirection of transport.

Once the “origin point” is established by the referencedcamera-alignment process, the two conveyance systems are articulated todetermine relative coordinates between each conveyance system's cameraand a reference point of the conveyance system (e.g., corresponding to aprinthead nozzle position for example), and this then permits a preciseidentification of any point relative to the printer's coordinate system,assuming a correct understanding as to the relationship (e.g.,orthogonality) between coordinate axes. As noted earlier, in such asystem, the printer's “understanding” of droplet landing locations isdependent on the print grid, which in turn is defined by this coordinatesystem; transport path motion error in such a system, if leftuncorrected, could potentially lead to a situation where a particularprint grid location (e.g., associated with an understanding of combinedspecific gripper/printhead position) deviates from actual position ofthese components. By correcting transport path error in the mannersdescribed herein, using the various devices described herein, thispermits the system to correct for that path error such that a substrateand printhead are each positioned in a manner corresponding to printgrid assumptions. In fact, as noted elsewhere herein, even errors suchas minor non-orthogonality between the transport paths can be correctedusing optional rotational offsets (e.g., non-zero values for θ₃ and θ₅)and/or, as previously mentioned, by adjusting optical guides (e.g.,optical beams for one or more transport paths) to correct fornon-orthogonality in the transport paths.

Continuing with the example provided by FIG. 3B, each substrate that isthen introduced into the system has one or more fiducials that areidentified and used to precisely understand position of the substrate(or a panel product thereon) during printing; as each substrate isintroduced, its fiducials are detected (e.g., using one or more of thecameras), and a mechanical system can be used to properly orient/alignthe substrate so as to correspond to an expected position (note thatthis process is not necessary for all embodiments, e.g., it is alsopossible to adjust printer control information, i.e., by modifying theprint recipe and/or firing triggers or particulars to accommodate knownsubstrate misalignment or disorientation).

The bottom portion of FIG. 3B shows how two linear transducers (e.g.,voice coils) on the gripper are driven to correct for rotational erroras well as positionally offset the substrate in a manner correspondingto an idealized edge (e.g., via displacement in the “x” dimension). Morespecifically, a localized portion of the transport path is designated bynumeral 327 as having a fair amount of curvature, which deviates from anidealized straight edge 109 of the transport path. At two effectivecontact points between the substrate and the transport path (designated“c₁” and “c₂,” respectively), this error is respectively assumed to be“x_(i)” (depicted as a offset relative to the idealized straight edge ina negative direction) and “x_(j)” (depicted as an offset relative to theidealized straight edge in a positive direction); here, it is assumedthat it is desired to precisely position a left edge of the substrate(or a printable area of the substrate) at absolute position “x_(k)” fromthe idealized transport path (e.g., corresponding to depicted virtualedge 323); numeral 105′ denotes a slight offset of the print grid so asto accommodate the entire range of “x” positional error imparted by thesystem and optionally provide some slight buffer. To effectuate thiscorrection, the positive error at position “c₁” (i.e., x_(i)) is furtheroffset by an amount of “x_(k)−|x_(i)|,” while the negative error atposition “c₂” (i.e., x_(j)) is further offset by an amount of“x_(k)+|x_(j)|.” The two depicted transducers “T” are controlled to thisend and so straighten the substrate relative to the idealized straightedge; similar corrections are performed at all other times duringmovement of the gripper along the transport path 107 in dependent onerror at the pertinent position, i.e., such that the substrate followsthe virtual path associated with absolute position “x_(k).”

Several points should be noted relative to this discussion. First,although the gripper is depicted in this FIG. as a single unit, in fact,it can consist of many parts (e.g., the aforementioned first and secondcomponents, or as a distributed series of 2, 3, 5 or another number ofgrippers or gripper components that engage the substrate at differentlocations). Second, while in this embodiment, the two transducers aredepicted as parallel linear actuators (e.g., each a voice coil orpiezoelectric transducer), this is not required for all embodiments.That is, depending on embodiment, the transducers “T” can be coupled inseries, and can be rotational, linear or other types of actuators; instill other embodiments, more than or fewer than two transducers can beused. Third, as noted above, a variety of mechanisms exist to identifyposition along the transport path, for example, a signal (e.g., drivesignal, timing signal, etc.) can be used for this purpose, as denoted bynumeral 328, or a position sensor 329 (such as a camera) can be used; inone specifically contemplated embodiment, as referenced above anddiscussed in U.S. Provisional Patent Application No. 62/459,402, aposition marking system and position detector is used for eachconveyance path, to measure and/or regulate associated position (e.g.,for printhead transport and substrate transport). Clearly, manyalternatives are possible.

As referenced earlier, a fabrication apparatus or system can havemultiple conveyance paths; in the context of a split-axis printer, inone embodiment as referenced earlier, a printer coordinate referencesystem can be defined in dependence on separate printhead and substratetransport paths. FIG. 3C is used to discuss positional error stemmingfrom inaccuracies in a second transport path such as the printheadtransport path. Such a context is generally depicted by numeral 351 inFIG. 3C. A substrate is advanced by a gripper in a first dimension(i.e., using one conveyance system, as represented by arrows 104) and aprinthead is advanced along a second transport path 356 in a seconddimension (i.e., using another conveyance system, as represented byarrows 354). At a first position 353 of the printhead along a transportpath associated with the latter conveyance system, the printheadexperiences error of Δi₀, Δj₀, and Δφ₀; note that the variables i, j andφ represent x and y offsets (and angular rotation in the xy plane), butthat i, j and φ are used instead of x, y and θ to distinguish thisexample from that of the gripper conveyance system. As denoted inphantom lines at the right side of the FIG., as the printhead isadvanced to position 353′, the error is Δi₁, Δj₁, and Δφ₁. Once again,this error is a function of position along the transport path 356, withchange in error potentially being linear or non-linear. If leftuncorrected, this error could also distort printing and create themanufacturing precision issues as referenced earlier. Note that in thisexample, it is assumed that any motion of the substrate 103 relative tothe gripper's transport path is corrected using the depicted gripper(and its transducers “T”), but the issue is that the printhead traveleralso might create error, resulting in x, y or θ error of the printhead,and which changes the expected landing positions of droplets ejectedfrom nozzles of the printhead. The effects of these errors areexemplified relative to an intended print grid 357 as indicated by arrow355, i.e., the effect of unintended printhead rotation (and/orunintended “x”-dimensional displacement) is seen via distorted printgrid 257′ (in analogous fashion, unintended printhead rotationdisplacement in the “y”-dimension would effectively result in a‘squeezing together’ of vertical print grid lines).

In the context of the FIG., it is also desired that the printheadexperience ideal motion, that is, motion uncharacterized by unintendedmechanical error. That is to say, in this example, it is desired thatthe printhead also follow a virtual, ideal (e.g., straight) transportpath 325, such as will effectively correspond to an unperturbed printgrid (e.g., denoted by numeral 357); this is achieved in one embodimentby causing the transported object (i.e., the printhead) to follow bothvirtual, “ideal” gripper motion, denoted by vertical line 109, as wellas virtual, “ideal” printhead motion, represented by horizontal line325.

In a manner much the same as with gripper path correction, a conveyancesystem for the printhead transport path can optionally also use anoptical guide (e.g., a laser source and associated optics/detectionsystem) and a set of transducers to facilitate idealized printheadpositioning; to this effect, responsive to dynamically-sensed error thetransducers advantageously provide displacement to an arbitrary“absolute” position that accommodates the entire range of “y” positionalerror of the printhead optionally provide some slight buffer, such thatthe printhead motion corresponds to a virtual path 369 that alsoprovides a fixed, known position corresponding to the “offset” printgrid (105′ from FIG. 3B).

FIG. 3D provides an illustration 361 of a system intended to redressthis type of error. That is, FIG. 3D shows a second transport path 356used to support lateral motion of one or more printheads, in the generaldirection indicated by arrows 354. A printhead assembly includes a first“track guided” component 363, which rides along the transport path 356(e.g., along a track or guide), and a second, offsettable component 364,which mounts the printhead(s). These first and second components areonce again operatively coupled by one or more transducers 365. Thetransducers in this example are each linear actuators which supportmicro-throws that offset the second component in the “y” dimension(and/or “z” dimension), with common-mode and differential mode driveonce again being used to selectively effectuate linear displacementand/or xy plane rotation (θ). As denoted by both numeral 367 and numeral367′ (each representing the printhead(s) at respective positions alongthe “cross-scan” or “x” dimension), correction permits the printhead(s)to follow a virtual ideal path 369 uncharacterized by mechanical error(i.e., even though the first component 363 continues to travel theerror-encumbered second transport path 356). An optical source 370 isonce again positioned to direct an optical beam 371 so as to detect andcorrect for jitter in a dimension orthogonal to the direction of theoptical beam; note that, depending on design (and size and/or availablespace on the printhead assembly), it may be desired to have the secondcomponent 364 mount the optical source and detect beam deviationrelative to stationary detector and/or optics (not shown in the FIG.)rather than detect motion of the detector and/or optics relative to astationary beam. Just as was the case with the gripper embodiment, thetransducers of FIG. 3D can be controlled to offset the printhead to anabsolute y position (i.e., corresponding to line 369) such that when theprinthead is at position 367, the aforementioned error of Δi₀, Δj₀, andΔφ₀ is further offset by Δi₂, Δj₂, and Δφ₂, and such that when theprinthead is at position 367′, the transducers are controlled to offsetthe printhead to add offset Δi₄, Δj₄, and Δφ₄; i and φ typically have aconstant value at position 367 and position 367′ and are both alsotypically zero, but again, this is not required for all embodiments.Just as with the prior gripper example, the depicted transducerconfiguration is exemplary only, and different transducers (e.g.,rotational transducers) can be used, and can be applied to differentconveyance systems and/or dimensions. Further, just as with the priorexample, the depicted transducers in this embodiment offset theprintheads using both common and differential mode control to effectuatea floating pivot point; the result is that a desired “error free”transport path 325 is offset to an arbitrary position 369, sufficient toencompass any “y” or in-scan dimensional jitter which is attributable toimperfections in the second transport path 356. As indicated by numeral355′, the result of these dynamically-applied corrections (and theoptional use of gripper corrections as referenced earlier) effectivelynormalizes the print grid, as indicated by numeral 357″. Note that asreferenced by function box 372, it is also possible to use anothertransducer 373 or to use drive signal correction techniques 374 and/orposition feedback/regulation techniques, as discussed earlier, to offsetposition of part or all of the printhead assembly to correct cross-scanpositional error.

Reflecting on the principles discussed thus far, correction of each ofthe substrate path to a “virtual,” straight edge, and the printhead pathto a “virtual,” straight edge, permits both of the substrate and theprinthead to be placed in a manner so as to conform to print gridassumptions (e.g., to the printer's coordinate reference system)notwithstanding fine error imparted by the mechanical systems. Thesetechniques may optionally be combined with drive control techniques (orother described techniques to correct each transported thing along itsdimension of transport) to further improve system accuracy. Once again,these techniques can also be extended to other motion dimensions andfabrication and/or mechanical systems as well.

FIG. 3E presents another example 375, namely, an alternative embodimentwhere error in one transport path can be corrected using one or moretransducers “T” associated with a second transport path. In this case,it can be assumed that a gripper assembly includes two lineartransducers that are controlled once again in common and differentialmodes to effectuate cross-scan offset and rotational correction withouta fixed pivot point. Note that in the case of this FIG., errors are onceagain micron or nanometer scale; the depicted angles and offsets arethus greatly exaggerated in the FIG. to assist with description. In thiscase, the FIG. shows icons for “two grippers,” although in reality theserepresent exactly the same gripper and position of the gripper along the“in-scan” dimension for two respective scans; in this case, however, oneof the conveyance paths (i.e., path 356, for the printhead assembly)does not have its own transducer-based error correction system (or, asan option, it does have such a system but the depiction corresponds toan implementation where the gripper's error correction system will befurther driven to correct for coordinate axis non-orthogonality). Thegripper's error correction system is thus controlled in this example toalso correct for printhead conveyance path jitter which is orthogonal tooptical beam 371, or for non-orthogonality between the transport paths;that is to say, detected deviation in the printhead conveyance path (ornon-orthogonality) is corrected in this example by adding additionmitigating offsets into the gripper's second component 303, e.g., bycombining deviations/error corrections from desired paths of multipleconveyance systems. In this embodiment, it should therefore be assumedthat the two grippers represent two alternate sets of transducer controlsignals that respectively correct for printhead system error (ornon-orthogonality) {Δi₀, Δj₀, and Δφ₀} at printhead position 373′ andprinthead system error (or non-orthogonality) {Δi₁, Δj₁, and Δφ₁} atprinthead position 373″ (i.e., corresponding to respective scans). Thatis, even though it was assumed in connection with FIG. 3B that grippertransport in the “y” dimension had been corrected to an ideal edge(relating to the gripper transport path), through the use of mitigatingoffsets and angles provided by the gripper systems' transducers, in oneembodiment, one may also correct for errors in the printhead path (orother errors) using these same transducers. As depicted, further offsetand/or rotations are added so as to effectively reposition the substrateso as to have the intended position and orientation relative to theprinthead (e.g., to produce motion in a way that matches printheaderror, as denoted by alternate transformed edges 107′″ and 107″″). Othererror correction techniques can also be applied to enhance theseprocesses.

As the forgoing discussion implies, while the previous examples showcorrection of error in one or two transport paths, the principlesdescribed in reference to FIG. 3E can be applied to correct for fineerror in any number of transport paths, e.g., one, two, three, four,five and so forth, with corrections for multiple transport paths beingapplied to a single drive path (e.g., to transducers used for substrateconveyance) or to correct errors in a first number of transport pathsvia mitigating corrections applied to a second, fewer number oftransport paths. As noted, this discussion also applies to correction ofnon-orthogonality, e.g., where the gripper and printhead transport pathsare not exactly at ninety degrees separation; this can be treated asequivalent to a case of measured printhead x-position-dependent error,with corresponding corrections applied by offsetting a transportedcomponent in either conveyance system. Note also, while the term“transport path” is exemplified in the figures as positional changealong a curvilinear path, the principles discussed above and fine errorcorrection procedures can also be applied to correct for fine error inany dimension, i.e., including rotation and accurate angularorientation—for example, in an embodiment where a mechanism is rotated,it is possible to measure “jitter” in angular rate of change ororientation, and to use transducers and/or drive signal correction asexemplified above to correct for such fine error. Finally, while FIG. 3Eshows the factoring of printhead transport path error (or othernon-gripper error) into gripper corrections, it is of contemplated thatthese various transport paths are interchangeable, e.g., gripper systempositional error can be corrected for using printhead systemerror-correction transducers.

FIG. 3F indicates the techniques presented above can be embodied in manydifferent forms to correct transport path error, as denoted generally bynumeral 381. In the context of a printer for manufacturing applications,a print recipe can be stored or cached in advance in a manner that willbe used to repeatably print, e.g., on many substrates on a successivebasis as part of an assembly-line-style process, as indicated by numeral382. As non-limiting examples, the techniques described herein can thenbe applied to correct for fine motion errors along paths associated withmotion of the substrate, motion of one or more printheads or printheadassemblies, motion of a camera assembly or inspection tool, and soforth. Note that one advantage of a system that is designed to driveerror to zero is that the effects of various other environmentalvariables such as temperature can be largely disregarded in terms oferror correction—path deviation, whatever the temperature, drives pathcorrections so that position and orientation during transport exactlyconform to the motion of the optical beam or guide. These techniquespermit automated correction of motion along these transport paths forfine error, such that motion of the substrate (or optionally, any ofthese systems) is made to correspond to an ideal path, notwithstandingthat the actual transport drive mechanism (e.g., motion of a gripper,edge guide, traveler, etc.) is still encumbered by path error whichimparts unintended offsets, non-linearities and other errors. Generallyspeaking, correction is done by a subsystem independent of the printrecipe, in a manner that permits print planning to assume that thesubstrate is ideally placed. For example, the structures describedherein in one embodiment provide means for counteracting an error orunintended offset “Δx” in a first dimension relative to a transportpath, where the first dimension is independent from the transport path(meaning it includes at least one component orthogonal thereto). Suchmeans can comprise at least one transducer that is controlled as afunction of transport path position to reduce or eliminate “Δx,” asdenoted by numeral 383 in FIG. 3F. Such means generally comprisestransducers that are electronically controlled to effectuate positionaldisplacement as a function of dynamic error that varies according toposition along the transport path, and/or other factors. As representedby numeral 384, these structures (or a different, potentiallyoverlapping set of structures) can provide means for defining a virtualedge at a specific, arbitrary position in the first dimension (e.g., at“x₃” in the embodiment from FIG. 3F) and offsetting a gripper componentrelative to the transport path (or a structure being transported) tosuch position; as before, such means also generally comprisestransducers and associated hardware and/or instructional logic thatcauses the transducers to negate or equalize error. Per numeral 385, inanother embodiment, the structures described herein provide means forcounteracting an error “Δy” in a second dimension relative to thetransport path; this second dimension is optionally independent from thetransport path, but it can also (instead) represent a common dimensionto the transport path or otherwise be generally synonymous with thetransport path. Such means can optionally comprise at least onetransducer that is controlled as a function of transport path position(and/or other factors) to reduce or eliminate “Δy” such as, for example,by correcting position of a transported “thing” for the embodimentdepicted above, or for otherwise adjusting velocity or motion along thetransport path, or using a position feedback system as referencedearlier. In yet another variation, per numeral 386, the same structuresthat might be applied to counteract “Δy” can provide means for defininga virtual edge at a specific (absolute or relative) position in thesecond dimension (e.g., at a non-zero “y₃,” relative to the embodimentabove) and offsetting the transport path (or a structure beingtransported) to such position; such means also generally comprisestransducers and logic to cause the transducers to effectuate positionaldisplacement as a function of dynamically-sensed error as an object isadvanced along the transport path. In one embodiment, this means canencompass another transport path or associated error correction system,e.g., an error correction system associated with printhead transport(e.g., so as to compensate for nozzle firing times, substrate, printheador other positional error, or other sources of error. In yet anotherembodiment (387), transducers similar to those discussed above can beapplied to counteract rotational error (Δθ); in one embodiment, thismeans can comprise a single transducer that converts electrical energyto structural rotation and, in other embodiments, two or more positionaltransducers can be applied to the same effect. For example, as discussedabove, one implementation can use two voice coils, each a lineartransducer, that when operated independently provide for rotationaladjustment of the thing being transported, with a floating, mechanicalpivot mechanism used to provide structural rigidity in support of thevoice coils. These structures (or a different, potentially overlappingset of structures) can also provide means for defining (388) a virtualedge at a specific (absolute or relative) angular relationship relativeto the first and second dimensions discussed above (e.g., at “θ₃” in theembodiment above) and for offsetting the transport path (or a structurebeing transported) in a manner corresponding to such an orientation. Instill another embodiment (389), structures described herein providemeans for counteracting an offset “Δz” in a third dimension relative toa transport path, where the third dimension is optionally independentfrom the transport path, as well as the first and second dimensionsreferenced above. Such means once again can comprise at least onetransducer that is controlled by hardware and/or software logic as afunction of dynamically measured error to reduce or eliminate thaterror; transducers and supporting logic can also be used to define avirtual edge at Z₃ (390). Per numeral 391 and an associated set ofellipses, these techniques can be applied to a multitude of degrees offreedom including correction of and/or offset in any of three positionaldimensions and any of three rotational dimensions (i.e., yaw, pitchand/or roll). In some embodiments, as represented by numeral 393, meansfor correcting for misalignment can be applied to align a substrate tothe printer's coordinate reference system; such means can includeposition sensor such as a camera, a handler or other transport device, aprocessor and associated support instructional and/or hardware logicthat repositions the substrate relative to desired printing (orconversely, adjusts printing to match a mal-aligned substrate). Pernumeral 395, means for correcting error in and/or aligning a printhead(PH) can include transducers with support for a floating pivot pointand/or common and differential correction modes, as referenced above.Per numeral 396, the system can also comprise means for realigning oradjusting the optical source (e.g., by adjusting attitude and yaw of thelaser), so as to provide for a calibrated path and/or printer coordinatereference system. A system can also include means (397) for correcting(non)-orthogonality of the coordinate reference system.

It should be noted that each of the referenced dimensional references,e.g., to the “x”, “y”, “θ” or other dimensions is arbitrary, that is,these can refer to any dimension and are not limited to Cartesian,angular, regular or rectilinear coordinates; in one embodiment, the “x”and “y” dimensions respectively correspond to the “cross-scan” and“in-scan” dimensions of a fabrication system, but this need not be thecase for all embodiments.

By correcting for motion error in such a manner, the described processesprovide for a “virtual” and/or ideal and/or straight transport path,notwithstanding that a mechanical motion system might still beencumbered, and might continue to track existent, repeatable flaws.Applied in the context of a manufacturing system, such as theaforementioned industrial printers, these techniques provide a powerfultool to enable precision positioning and manufacturing.

II. On-Line and Off-Line Processes Associated with a Split-AxisManufacturing System

FIGS. 4A-5 are used to discuss some specifics associated with a typicalsplit-axis fabrication system. FIG. 4A is used to discuss typicalscanning motion used in thus a fabrication system to deposit materialthat will form a layer of an electronic device, while FIG. 4B is used todiscuss configuration of a specific manufacturing system that relies ona printer and processing chamber. FIG. 4C will be used to discuss aprocess in which each substrate in a series of substrates is alignedwith a coordinate reference system used by a printer, while FIG. 5 willbe used to discuss the process of fabricating an electronic device (or aspecific layer of such a device).

More particularly, FIG. 4A depicts a substrate 401, with a number ofdashed-line boxes representing individual panel products. One suchproduct, seen in the bottom left of the FIG., is designated usingreference numeral 402. Each substrate (in a series of substrates) in oneembodiment has a number of alignment marks, such as represented bynumeral 403. In one embodiment, two such marks 403 are used for thesubstrate as a whole, enabling measurement of substrate positionaloffset relative to mechanical components of the printer (e.g., thegripper) and, in another embodiment, three or more such marks 403 areused to facilitate additional adjustments (e.g., rotational adjustment).In yet another embodiment, each panel (such as any of the four depictedpanels) is accompanied by per-panel alignment marks, such as marks 405;this latter scheme permits gripper adjustment so that the individualpanel being printed is precisely aligned to the printer's coordinatereference system. Whichever scheme is used, one or more cameras 406 areused to image the alignment marks in order to identify substrateposition relative to the printer's coordinate reference system; in oneembodiment, cameras are mounted to each of the gripper and the travelingprinthead assembly, and these cameras can be respectively controlled soas to image substrate one or more substrate fiducials and identifyprecise substrate (and/or product) position and orientation relative topositions along the printer's axes of transport (i.e., relative to theprinter's coordinate reference system). In another contemplatedembodiment, a single motionless camera is used, and the transportmechanism of the printer (e.g., a handler and/or air flotationmechanism) moves the substrate to position each alignment mark insequence in the field of view of the single camera; in a differentembodiment, the camera is mounted on a two dimensional motion system fortransport relative to the substrate. In yet other embodiments, low andhigh magnification images are taken, the low magnification image tocoarsely position a fiducial for high resolution magnification, and thehigh magnification image to identify precise fiducial position accordingto a printer coordinate system; a line or CCD scanner can also be used.Reflecting on the earlier discussion, in one embodiment, the transportmechanism(s) of the printer (and associated feedback/position detectionmechanisms) control(s) motion to within about a micron of intendedposition, with the imaging system used per-substrate to align (and tooptionally mechanically reposition) the substrate to the printer'scoordinate reference system until reasonably-accurate alignment isachieved; in another embodiment, measured positional error and/ororientation error can be used to customize/adjust the print recipe, insoftware, such that printing is distorted so as to match the detectedsubstrate position/orientation.

In a typical implementation, printing will be performed to deposit agiven material layer on the entire substrate at once (i.e., with asingle print process providing a layer for multiple products). Note thatsuch a deposition can be performed within individual pixel wells (notillustrated in FIG. 4A, i.e., there would typically be millions of suchwells for a television screen) to deposit light generating layers withinsuch wells, or on a “blanket” basis to deposit a barrier or protectivelayer, such as an encapsulation layer. Whichever deposition process isat issue, FIG. 4A shows two illustrative scans 407 and 408 along thelong axis of the substrate; in a split-axis printer, the substrate istypically moved back and forth (e.g., in the direction of the depictedarrows) with the printer advancing the printhead positionally (i.e., inthe vertical direction relative to the drawing page) in between scans.Note that while the scan paths are depicted as linear, this is notrequired in any embodiment. Also, while the scan paths (e.g., 407 and408) are illustrated as adjacent and mutually-exclusive in terms ofcovered area, this also is not required in any embodiment (e.g., theprinthead(s) can be applied on a fractional basis relative to a printswath, as necessary or desired). Finally, also note that any given scanpath typically passes over the entire printable length of the substrateto print a layer for multiple products in a single pass. Each pass usesnozzle firing decisions according to the print recipe, with control overthe transducers (not shown in FIG. 4A) used to ensure that each dropletin each scan is deposited precisely where it should be relative tosubstrate and/or panel boundaries.

FIG. 4B shows one contemplated multi-chambered fabrication apparatus 411that can be used to apply techniques disclosed herein. Generallyspeaking, the depicted apparatus 411 includes several general modules orsubsystems including a transfer module 413, a printing module 415 and aprocessing module 417. Each module maintains a controlled environment,such that printing for example can be performed by the printing module415 in a first controlled atmosphere and other processing, for example,another deposition process such an inorganic encapsulation layerdeposition or a curing process (e.g., for printed materials), can beperformed in a second controlled atmosphere; these atmospheres can bethe same if desired. The apparatus 411 uses one or more mechanicalhandlers to move a substrate between modules without exposing thesubstrate to an uncontrolled atmosphere. Within any given module, it ispossible to use other substrate handling systems and/or specific devicesand control systems adapted to the processing to be performed for thatmodule. Within the printing module 415, as discussed, mechanicalhandling can include use (within a controlled atmosphere) of a flotationtable, gripper, and alignment/fine error correction mechanisms, asdiscussed above.

Various embodiments of the transfer module 413 can include an inputloadlock 419 (i.e., a chamber that provides buffering between differentenvironments while maintaining a controlled atmosphere), a transferchamber 421 (also having a handler for transporting a substrate), and anatmospheric buffer chamber 423. Within the printing module 415, it ispossible to use other substrate handling mechanisms such as a flotationtable for stable support of a substrate during a printing process.Additionally, a xyz-motion system (such as a split-axis or gantry motionsystem) can be used to reposition and/or align the substrate to theprinter, to provide for precise positioning of at least one printheadrelative to the substrate, and to provide a y-axis conveyance system forthe transport of the substrate through the printing module 415. It isalso possible within the printing chamber to use multiple inks forprinting, e.g., using respective printhead assemblies such that, forexample, two different types of deposition processes can be performedwithin the printing module in a controlled atmosphere. The printingmodule 415 can comprise a gas enclosure 425 housing an inkjet printingsystem, with means for introducing a non-reactive atmosphere (e.g.,nitrogen or a noble gas) and otherwise controlling the atmosphere forenvironmental regulation (e.g., temperature and pressure, gasconstituency and particulate presence).

Various embodiments of a processing module 417 can include, for example,a transfer chamber 426; this transfer chamber also has a including ahandler for transporting a substrate. In addition, the processing modulecan also include an output loadlock 427, a nitrogen stack buffer 428,and a curing chamber 429. In some applications, the curing chamber canbe used to cure, bake or dry a monomer film into a uniform polymer film;for example, two specifically contemplated processes include a heatingprocess and a UV radiation cure process.

In one application, the apparatus 411 is adapted for bulk production ofliquid crystal display screens or OLED display screens, for example, thefabrication of an array of (e.g.) eight screens at once on a singlelarge substrate. The apparatus 411 can support an assembly-line styleprocess, such that a series of substrates is processed in succession,with one substrate being printed on and then advance for cure while asecond substrate in the series is concurrently introduced into theprinting module 415. The screens manufactured in one example can be usedfor televisions and as display screens for other forms of electronicdevices. In a second application, the apparatus can be used for bulkproduction of solar panels in much the same manner.

The printing module 415 can advantageously be used in such applicationsto deposit organic light generating layers or encapsulation layers thathelp protect the sensitive elements of OLED display devices. Forexample, the depicted apparatus 411 can be loaded with a substrate andcan be controlled to move the substrate between the various chambers ina manner uninterrupted by exposure to an uncontrolled atmosphere duringthe encapsulation process. The substrate can be loaded via the inputloadlock 419. A handler positioned in the transfer module 413 can movethe substrate from the input loadlock 419 to the printing module 415and, following completion of a printing process, can move the substrateto the processing module 417 for cure. By repeated deposition ofsubsequent layers, each of controlled thickness, aggregate encapsulationcan be built up to suit any desired application. Note once again thatthe techniques described above are not limited to encapsulationprocesses, and also that many different types of tools can be used. Forexample, the configuration of the apparatus 411 can be varied to placethe various modules 413, 415 and 417 in different juxtaposition; also,additional, fewer or different modules can also be used. In oneembodiment, the depicted apparatus 411 can be daisy-chained with othermodules and/or systems, potentially to produce other layers of thedesired product (e.g., via different processes). When a first substratein a series is finished (e.g., has been processed to deposit materialthat will form the layer in-question), another substrate in the seriesof substrates is then introduced and processed in the same manner, e.g.,according to the same recipe.

While FIG. 4B provides one example of a set of linked chambers orfabrication components, clearly many other possibilities exist. Thetechniques introduced above can be used with the device depicted in FIG.4B, or indeed, to control a fabrication process performed by any othertype of deposition equipment.

Once printing is finished, the substrate and wet ink (i.e., depositedliquid) can then be transported for curing or processing of thedeposited liquid into a permanent layer. For example, a substrate canhave “ink” applied in a printing module 415, and then be transported toa curing chamber 429, all without breaking the controlled atmosphere(i.e., which is advantageously used to inhibit moisture, oxygen orparticulate contamination). In a different embodiment, a UV scanner orother processing mechanism can be used in situ, for example, being usedon split-axis traveler, in much the same manner as the aforementionedprinthead/camera assembly.

FIG. 4C provides another flow chart relating to system alignment, with aseries of steps being generally designated using numeral 431. The methodbegins with system initialization, per numeral 432; for example, thisinitialization can be performed at each power-up, or on an ad-hoc (e.g.,operator-commanded) or periodic basis. An alignment/detection operation433 is thereafter performed for the various conveyance paths, forexample, to identify a common point as an origin or common point ofreference, and to identify precise position of each nozzle within thecoordinate reference system established by this point and the positionalfeedback (and position indicators) associated with each transport path;as indicated at the left side of the FIG. this operation (or systeminitialization) can be performed if desired following a maintenanceoperation, for example, resulting in a change of the printheads or othersystem components (e.g., which might result in nozzles at differentlocations relative to the printer's coordinate reference system. Notethat numeral 434 represents a typical printhead assembly configuration,i.e., where the assembly mounts nine printheads (this may be one largeassembly or a number of subassemblies, for example, three “ink-sticks”that each mount three printheads in a staggered configuration). In oneembodiment, there can be 256-1024 nozzles per printhead.

Elaborating on the alignment procedure, and as described by U.S.Provisional Application No. 62/459,402, a detachable optical reticle canbe attached in a known position (e.g., coaxially) with a“downward-facing” camera of the printhead assembly, and the both thegripper and the printhead are articulated along their transport pathsuntil this camera and an “upward-facing” camera mounted to the gripper“find” each other (i.e., they both image the reticle, for example, theyare positioned until each camera image finds the reticle or anassociated set of crosshairs directly in the associated, capturedimage). This point can then be used to define a common reference pointor origin point of the coordinate reference system, as represented bynumeral 435. Each axis of transport is then moved so that one of thesecameras images a fiducial associated with the other conveyance system.For example, per numeral 437, the gripper and printhead conveyancesystems are articulated until the gripper's “upward-facing” camera findsa fiducial or alignment mark of the printhead, and using a searchalgorithm, precisely locates the center point of each print nozzle. Theposition of each motion system—gripper/printhead assembly—along itsrespective transport path (e.g., in observation of precise positionalplacement facilitated by alignment marks from an optical tape) thenpermits precise definition of this fiducial or alignment mark in theprinter's coordinate reference system, and so forth. Each nozzle can beprecisely defined in terms of the printer's coordinate reference system,enabling accurate control over where droplets are ejected. Relative toother potential sources of error, e.g., unintended non-orthogonalitybetween transport axes, this error can be detected using additionalfiducials or alignment marks (e.g., a fixed fiducial associated with theprinter support table is image by one or both cameras, per numeral 439,with associated adjustments made to the coordinate reference system,optical guide system, or the recipe, or alternatively, the opticalguide/laser can be adjusted as part of a manual or electroniccalibration process, per numeral 440, until precise alignment andorthogonality are achieved.

Optionally, such a calibration process can be performed periodically orany time system parameters are changed, e.g., a new printhead isintroduced, potentially introducing nozzles at previously knownlocations relative to the printer's coordinate reference system.

During run time, the introduction of each substrate in a series ofsubstrates may potentially introduce unintended misalignment betweenwhere printing is supposed to occur (relative to the printer) and whereprinting does occur (relative to the substrate). Each substrate istherefore subjected to an position and/or orientation detection process,per numeral 441, with associated error being factored into electronicprint particulars or to reposition the given substrate for printing of alayer (so that printing occurs in in precise registration relative tosubstrate fiducials and relative to other layers deposited on thesubstrate which are also in precise registration relative to thosefiducials). Per numeral 442, as each given substrate in the series isintroduced into the printing module (e.g., 415 from FIG. 4B), it isfirst roughly aligned using one or more bankers and/or mechanicalhandlers. With the given substrate and its associated fiducials inapproximately the correct position, an imaging system (such as the“downward-facing” camera system mounted by the printhead assembly) isthen employed, using a search algorithm and suitable image processing,to precisely find one or more substrate fiducials, per numeral 443. Forexample, this detection can be performed using a spiral or similarsearch pattern which searches about a fiducial expected position untilprecise fiducial position and/or orientation has been detected. A seriesof optional and/or alternative correction processes can then be employedso as to precisely position and/or reposition the substrate; forexample, as indicated variously by process box 445, in one embodiment,the aforementioned transducers can be driven so as to provide precisesubstrate positioning (e.g., a vacuum lock of the gripper's “secondcomponent” is not adjusted, but the transducers are articulated incommon- and/or differential-drive modes until the substrate fiducial hasexactly the right start position and orientation. The transducerpositions corresponding to this substrate position/orientation can thenbe used as a zero level or position, with error corrections (duringproduction) then superimposed thereon or otherwise defined relative tothese positions. Alternatively or in addition, a mechanical handler canbe used to reposition the substrate as necessary. As still anotheralternative, the recipe can be adjusted in software, as disclosed in USPatent Publication No. 20150298153, to correct for alignment error(e.g., with correction for repeatable error left for transducersassociated with the gripper and/or printhead conveyance systems, asreferenced earlier). Per numeral 445, printing then occurs according tothe desired print recipe; following printing, the just-printed substrateis unloaded for cure (e.g., it is transported to a processing chamber),while the system receives or prepares to receive a new substrate underrobotic- or human-direction.

FIG. 5 represents a number of different implementation tiers,collectively designated by reference numeral 501; each one of thesetiers represents a possible discrete implementation of the techniquesintroduced herein. First, techniques as introduced in this disclosurecan take the form of instructions stored on non-transitorymachine-readable media, as represented by graphic 503 (e.g., executableinstructions or software for controlling a computer or a printer).Second, per computer icon 505, these techniques can also optionally beimplemented as part of a computer or network, for example, within acompany that designs or manufactures components for sale or use in otherproducts. Third, as exemplified using a storage media graphic 507, thetechniques introduced earlier can take the form of a stored printercontrol instructions, e.g., as data that, when acted upon, will cause aprinter to fabricate one or more layers of a component dependent on theuse of different ink volumes or positions to mitigate alignment error,per the discussion above. Note that printer instructions can be directlytransmitted to a printer, for example, over a LAN; in this context, thestorage media graphic can represent (without limitation) RAM inside oraccessible to a computer or printer, or a portable media such as a flashdrive. Fourth, as represented by a fabrication device icon 509, thetechniques introduced above can be implemented as part of a fabricationapparatus or machine, or in the form of a printer within such anapparatus or machine. It is noted that the particular depiction of thefabrication device 509 represents one exemplary printer device, forexample, as discussed in connection with the FIG. 4B. The techniquesintroduced above can also be embodied as an assembly of manufacturedcomponents; in FIG. 5 for example, several such components are depictedin the form of an array 511 of semi-finished flat panel devices thatwill be separated and sold for incorporation into end consumer products.The depicted devices may have, for example, one or more light generatinglayers or encapsulation layers or other layers fabricated in dependenceon the methods introduced above. The techniques introduced above canalso be embodied in the form of end-consumer products as referenced,e.g., in the form of display screens for portable digital devices 513(e.g., such as electronic pads or smart phones), as television displayscreens 515 (e.g., OLED TVs), solar panels 517, or other types ofdevices.

Having thus discussed in detail sources of positional error andassociated remedies, this disclosure will now turn to discussion of amore detailed embodiment of a specific fabrication apparatus.

III. Specific Implementations

FIGS. 6A-6E are used to discuss specific printer implementations,namely, as applied to the manufacture of OLED display or solar panels.Depending on product design, the printer seen in these FIGS. can be usedto deposit a layer for an array of products at-once on a substrate(e.g., many smart phone or other portable device displays, perhapshundreds at a time, such as conceptually represented by the individual,arrayed products on substrate 411 from FIG. 4A), or a single product persubstrate such as the display screen of the HDTV 415 or solar panel 417from FIG. 4A. Many other example applications will be apparent to thosehaving skill in the art.

More specifically, FIG. 6A shows a printer 601 as having a number ofcomponents which operate to allow the reliable placement of ink dropsonto specific locations on a substrate. Printing in the illustratedsystem requires relative motion between each printhead assembly and thesubstrate. This can be accomplished with a motion system, typically agantry or split-axis system. Either a printhead assembly can move over astationary substrate (gantry style), or both the printhead assembly andsubstrate can move, in the case of a split-axis configuration. Inanother embodiment, a printhead assembly can be substantially stationarywhile the substrate is moved along both x- and y-axes relative to theprintheads.

The printer comprises a printer support table 603 and a bridge 605; theprinter support table 603 is used to transport substrates (such assubstrate 609) using a planar flotation support surface mounted by aframe 604, while the bridge 605 is used for transport of a number ofprintheads and various support tools, for example, an optical inspectiontool, cure device, and so forth. As noted earlier, a gripper (e.g., avacuum gripper, not seen in this FIG.) provides a “fast axis” forconveying the substrate (e.g., in what is referred to elsewhere hereinas the “y” dimension, see, e.g., dimensional legend 602), while thebridge permits one or more printhead assemblies 611A and 611B (and/orcameras) to move back and forth along the bridge 605 along a “slowaxis.” To effectuate printing, a printhead assembly (e.g., the primaryassembly 611A) will be positioned at a suitable position along thebridge while the vacuum gripper moves the substrate in a generallylinear manner along the “y” dimension, to provide for a first scan orraster; the printhead assembly 611A or 611B is then typically moved to adifferent position along the bridge 605 and stopped, with the vacuumgripper then moving the substrate 609 back in the opposite directionunderneath the new printhead assembly position, and so forth, to providean ensuing scan or raster, and so forth.

The printer support table 603 can have a porous medium to provide forthe planar floatation support surface. The planar flotation supportsurface includes an input zone, a print zone and an output zone, whichare respectively designated using numerals 606-608; the substrate 609 isdepicted in the input zone 606, ready to be printed on. A combination ofpositive gas pressure and vacuum can be applied through the arrangementof ports or using a distributed porous medium provided by the supporttable. Such a zone having both pressure and vacuum control can beeffectively used to provide a fluidic spring between the flotation tablesurface and each substrate 609. A combination of positive pressure andvacuum control can provide a fluidic spring with bidirectionalstiffness. The gap that exists between the substrate 609 and the surfaceof the flotation table can be referred to as the “fly height,” with thisheight regulated by controlling the positive pressure and vacuum portstates. In this manner, a z-axis height of the substrate can becarefully controlled at various parts of the printer support table,including without limitation, in the print zone 607. In someembodiments, mechanical retaining techniques, such as pins or a frame,can be used to restrict lateral translation of the substrate while thesubstrate is supported by the gas cushion. Such retaining techniques caninclude using spring loaded structures, such as to reduce theinstantaneous forces incident the sides of the substrate while thesubstrate is being retained; this can be beneficial as a high forceimpact between a laterally translating substrate and a retaining meanscould potentially cause substrate chipping or catastrophic breakage. Atother regions of the printer support table, the fly height need not beas precisely controlled, for example, in the input or output zones 606and 608, or it can be controlled to provide a different fly height orfly height profile. A “transition zone” between regions can be providedsuch as where a ratio of pressure to vacuum nozzles increases ordecreases gradually. In an illustrative example, there can be anessentially uniform height between a pressure-vacuum zone, a transitionzone, and a pressure only zone, so that within tolerances the threezones can lie essentially in one plane. A fly height of a substrate overpressure-only zones elsewhere can be greater than the fly height of asubstrate over a pressure-vacuum zone, such as in order to allow enoughheight so that a substrate will not collide with a printer support tablein the pressure-only zones. In an illustrative example, an OLED panelsubstrate can have a fly height of between about 150 microns (μ) toabout 300μ above pressure-only zones, and then between about 30μ toabout 50μ above a pressure-vacuum zone. In an illustrative example, oneor more portions of the printer support table 603 or other fabricationapparatus can include an air bearing assembly provided by NewWay AirBearings (Aston, Pa., United States of America). A porous medium can beobtained such as from Nano TEM Co., Ltd. (Niigata, Japan), such ashaving physical dimensions specified to occupy an entirety of thesubstrate 609, or specified regions of the substrate such as displayregions or regions outside display regions. Such a porous medium caninclude a pore size specified to provide a desired pressurized gas flowover a specified area, while reducing or eliminating mura or othervisible defect formation.

In the example of FIG. 6A, a handler or other conveyance system (notshown) delivers each substrate 609 to the input region 606 of theprinter support table 603. The vacuum gripper engages the substrate 609,transports it from the input zone 606 into the print zone 607 and thenmoves the substrate back-and-forth for printing, to effectuaterespective “near-frictionless,” low-particle-generating, high-speedscans along the fast axis of the printer, according to the particularrecipe. When printing is finished, the vacuum gripper then transportsthe substrate to the output zone 608, where a mechanical handler takesover and conveys the substrate to the next processing apparatus; duringthis time, a new substrate can be received in the input zone 606, andthe vacuum gripper is then transported back to that zone to engage thatnew substrate. In one embodiment, deposited droplets of ink are allowedto meld together in the output zone, e.g., via a brief rest or settlingperiod during which the substrate is allowed to remain in the outputzone, with printing and settling and ensuing cure being performed within a controlled environment (e.g., generally in a nitrogen or noble gasatmosphere, or other non-reactive environment).

The depicted printer 601 also can include one or more maintenance ormanagement bays 612A and 612B, each of which can store tools 615-620 formodular engagement by one or both printhead assemblies, for example,printheads, cameras, “ink sticks;” similarly, in one embodiment, thesebays are configured for interaction with other components, such as adroplet measurement module, a purge basin module, a blotter module, andso forth, optionally within the same enclosed space (enclosure volume)or a second volume. In one embodiment, a printhead assembly cansimultaneously mount three “ink sticks,” as denoted by numeral 622, witheach “ink stick” supporting three printheads and supporting fluidics andcircuit contacts in a manner adapted for modular engagement with theprinthead assembly. The ink delivery system (not separately shown inFIG. 6A) comprises one or more ink reservoirs, ink supply tubing toconvey ink between the reservoirs and one or more of the printheadassemblies, and suitable control circuitry, while the motion system(also not separately shown in FIG. 6A) comprises electronic controlelements, such as a subsystem master processor and control systems andactuating elements for the gripper and printhead assemblies, andsuitable control code.

The printhead assemblies 611A/611B each comprise a traveler 623A/623Bwhich rides along the bridge (i.e., on a track or guide) and anengagement mechanism 624A/624B mounted proximate to a front surface625A/625B of the bridge to robotically engage and disengage each of theink sticks or other tools on a modular basis as desired with eachsupport bay 612A/612B. Each printhead assembly (611A/611B) is supportedby a linear air bearing motion system (which is intrinsicallylow-particle generating) or other linear motion system to allow it tomove along the bridge 605. Each printhead assembly is accompanied byfluidic and electronic connections to at least one printhead, with eachprinthead having hundreds to thousands of nozzles capable of ejectingink at a controlled rate, velocity and size. To provide one illustrativeexample, a printhead assembly can include between about 1 to about 60printhead devices, where each printhead device can have between about 1to 90 printheads, with each printhead having 16 to about 2048 nozzles,each capable of expelling a droplet having of volume of about 1-to-20picoLiters (pL) depending on design. The front surfaces 625A/625B eachprovide for a respective z-axis moving plate which controls height ofthe engagement mechanism (and thus printheads or other tools) above asurface of the substrate. The traveler and engagement mechanism canserve as the “first” and “second” components referenced earlier for theprinthead assembly, e.g., these components in one embodiment are coupledby an electromechanical interface (not seen in FIG. 6A) which permitsrobotic adjustment of the transported tool in each of x, y and zdimensions. In this regard, U.S. Provisional Patent Application No.62/459,402, referenced earlier, provides details relating to z-axiscalibration of printheads and various other elements of the printer'scoordinate reference system in general. The electromechanical interfacecan advantageously include stepper motors, fine adjustment screws andother mechanisms for adjusting (a) x, y and/or z mounting of each toolrelative to the relevant engagement mechanism, and (b) pitch betweenrespective tools (e.g., pitch between ink sticks). In addition, eachtool can also include various fine adjustment mechanisms, e.g., forpitch adjustment between multiple printheads carried by each ink stick.The electromechanical interface can include a kinematic or similar mountfor repeatably and reliably engaging each tool to within a micron ofintended position in each dimension, with robotic adjustment mechanismsoptionally configured to provide feedback for precise positionadjustment of each tool relative to the engagement mechanism.

The electromechanical interface advantageously also includes a set oftransducers as referenced earlier, e.g., to offset the engagementmechanism 624A/624B linearly in the “y” dimension relative to theassociated traveler 623A/623B. As should be apparent from the discussionthus far, provision of a transducer correction mechanism to provide a“virtual straight edge” for the printhead(s) and provision of atransducer correction mechanism to provide another “virtual straightedge” for the gripper (not seen in FIG. 6A) facilitates a print gridwhich is more “regular,” e.g., it helps ensure uniform droplet placementat precise, regular spacings associated with the print grid, therebypromoting enhanced layer uniformity.

As should be apparent, the depicted structural elements permit controlover substrate x-axis position using common mode displacement of thesubstrate by the respective voice coil assemblies, as well as controlover orientation of the substrate about the 0 dimension (i.e., rotationabout the z-axis). Various embodiments of the depicted gripper systemcan maintain the orientation of a substrate parallel to the y-axis oftravel to within +/−4300 micro-radians, or less, depending onimplementation. As mentioned earlier, when it is also desired to adjustsubstrate position to further match deviations in printhead (printheadassembly) position and orientation, this control over orientationtogether with common mode x-axis displacement, and the effectiveimplementation of a floating pivot point for the substrate, permitprecision repositioning of the substrate to simulate perfect, virtualedges (or guides) for each of substrate motion and traveler motion(e.g., printhead, camera, etc.). As noted earlier, each of the vacuumgripper and the printhead assembly/traveler also includes an opticalsystem (not seen in the FIG.) for detecting alignment marks, i.e., toprovide an electronic position signal that indicates with precisionlocation of the gripper or printhead assembly along the associatedtransport path.

As should be observed, the use of voice coils in conjunction with air(gas) bearing support of a substrate, as well the vacuum basedengagement between the gripper and substrate, provide an efficientmechanism for a frictionless, effective mechanism for both transportingand fine tuning position of a substrate. This structure helps maintaincontact-minimized interaction with the substrate during electroniccomponent fabrication (e.g., during layer deposition and/or cure), whichhelps avoid distortions and defects which could otherwise be engenderedas a result of substrate deformation, localized substrate temperaturefluctuation induced by contact, or other effects such as electrostaticenergy buildup. At the same time, a near frictionless support andtransducer system, in combination, help provide micron-scale or betterthrows used to perform fine tuning of substrate position. Thesestructures help perform precise substrate corrections necessary toobtain one or more “virtual transport paths,” notwithstanding mechanicalimperfections as referenced earlier, and notwithstanding that asubstrate that serves as the deposition target may be meters long andmeters wide. The voice coils can also be configured to provide arelatively large throw, for example, from sub-micron to one hundredmicrons or more, which may be important depending on implementation(e.g., when a system at issue, given its manufacturing tolerances,experiences jitter of this magnitude).

FIG. 6B shows a vacuum gripper 631 in additional detail. The vacuumgripper 631 once again comprises a first component 633 (which rides atopa y-axis carriage, not seen in the FIG.), a second component 635 whichengages substrates, and two linear transducers 637 and 639. Note that asdepicted, the second component sits vertically above the first componentas both are advanced along the gripper's direction of transport (e.g.,along the “y-dimension” depicted by legend 632); the second componentsupports a vacuum chuck 643 that is used to selectively engagesubstrates. Unlike previous examples predicated on the use of a virtualpivot point, this example further includes a floating mechanical pivotassembly or mechanism 641 which provides a mechanical linkage betweenthe first and second components 633/635 as the gripper is advanced alongthe y-dimension and helps provide structural support for embodimentswhere the linear transducers are embodied as voice coils. The floatingpivot mechanism includes a pivot shaft 651, an assembly upper plate 653(which is mounted to the gripper's second component 635) and an x-axissliding lower plate 655 which moves on rails relative to a support frame644 provided by the gripper's first component 633. The assembly upperplate preferably is made of a relatively thin material to provideflexure, for example, to permit leveling of the gripper's secondcomponent relative to the substrate and the floatation table, and isrigidly affixed to the second gripper's second component using mountingbrackets 656. Succinctly stated, as component 633 is advanced along they-dimension, the floating mechanical pivot mechanism 641 constrains thecomponent 635 to also advance along the y-dimension while permittingx-axis sliding interaction between these components 633/635 and rotationabout a floating pivot axis 649.

The floating pivot point permits differential- or common-mode drive ofthe transducers 637 and 639, as discussed previously; these variousmotions are further represented by sets of motion arrows 645/647.Generally speaking, each transducer couples a mounting block 657 (e.g.,mounted relative to frame 644 of the gripper's first component) and amounting plate 661 (mounted to the gripper's second component), with alinear actuator 659 coupling the mounting block and the mounting plateand providing precise displacement along the x-axis. As denoted bydashed-line outlines 663 and 665, the design of the transducers 637/639and floating mechanical pivot mechanism 641 will be shown and discussedin greater detail in connection with FIGS. 6C and 6D.

FIG. 6B also illustrates positioning of an optical guide 667 relative tothe various components of the gripper. In this design, the beam of lightis above a top surface of the offsettable component (635) of thegripper, but below a plane occupied by the substrate; such aconfiguration promotes ease of access for purposes of adjusting opticalcomponents for purposes of proper alignment. In alternative embodiments,the optical guide (i.e., the beam of light in this example) can bedirected within a cavity between the gripper's first and secondcomponents 633/655 and thus is seen in semi-dashed line where the beamcrosses the gripper, to denote that the beam can be hidden from view atthis particular location in such an alternate embodiment, e.g., asdenoted by numeral 667′. A beam splitter 668 for each transducer is alsomounted to the gripper's second component 635, and is used to redirectlaser light from the optical guide to a detector for each transducer,represented by numeral 669. The design of the beam splitter and/or thedetector 668/669 for each transducer advantageously features adjustmentscrews to adjust each, e.g., such that the beam splitter and/or detectorbeing can be aligned such that the detector reads zero error when thegripper's second component is ideally positioned relative to apreviously-aligned optical guide (667). These various elements are alsomounted, in one embodiment, to the top surface of the gripper'soffsettable component 635, but below a plane occupied by the substrate;in alternative embodiments, these elements can be mounted elsewhere(e.g., in between components 633 and 635, i.e., beneath the top surfaceof component 635, in a manner hidden from view. The beam splitter,detector and adjustment screws are each advantageously positioned so asto be accessible (e.g., using a screwdriver or other tool) so as topermit offline adjustment for purposes of this calibration. In alternateembodiments, proper beam splitter and/or detector alignment can bedetected, or misalignment can be detected and factored in to thecorrection process in other ways; for example, in one embodiment, a testsubstrate can be introduced, fiducials on the test substrate can beimaged at multiple locations, and a misaligned optical beam, beamsplitter and/or detector can have readings at different transport pathadvancement positions stored and factored into the error correctionprocess at run-time, with transducer correction signals effectivelybeing “skewed” at run time so that the gripper's second componenttravels ideally, e.g., based on preprogrammed adjustments to readings ofa misaligned optical guide or associated optical components. It mustalso be pointed out that in various other embodiments, the opticalcomponents can be configured differently, e.g., a detector can bemounted separately from the gripper, and/or the optical source can bemounted to the transported component and/or the various components canbe mounted in other locations.

Notably, FIG. 6B also shows an “upward-facing” camera 670, which asstated earlier is used to image a fiducial via a focal path 669(represented as an optical cone in the FIG.) for purposes of aligningthe vacuum gripper and printhead assembly (not shown) to define theprinter's coordinate reference system, and to identify relative distanceand position of various printhead assembly components (e.g., preciseprinthead nozzle position and the printhead assembly camera, not shownin the FIG., in terms of the printer's coordinate reference system).

FIG. 6C shows an enlarged view of the linear transducer 637 from FIG.6B. Once again, the other transducer (designated by numeral 639 in FIG.6B) is generally identical or symmetrical in design to the transducer637.

More particularly, the linear transducer in this example is predicatedon a voice coil design with first and second components 633/635 of thegripper supported on an air bearing. The voice coil is contained withina cylindrical housing 659 to permit displacement of the second component(e.g., the vacuum chuck bar and substrate) relative to the secondcomponent along the general direction of double arrows 645. A adjustmentplate 670 advantageously permits fine adjustments of transducer xyzorientation as between these two components, so as to linearly move thesecond components along the x-dimension axis (see dimensional legend 632in FIG. 6B); once again, this can provided for with a configuration ofmanually adjustable screws that are adjusted and/or calibratedinfrequently. The voice coil in this embodiment has a magnet-baseddesign that provides for fast, accurate microscopic throws to displacethe mounting plate 661 toward and away from the mounting block 657 as afunction of an electronic control signal, i.e., once again, in thedirection of double arrows 645.

FIG. 6D shows the floating, mechanical pivot mechanism 641 from FIG. 6B.As noted earlier, an assembly upper plate 653 carries a bushing whichpermits pivot of the assembly upper plate (and the gripper's secondcomponent and vacuum chuck) about a pivot axis 649. This axis is definedby a pivot shaft 651 which extends vertically downward parallel to thez-dimension, and which couples to the x-axis sliding lower plate 655.Although not seen in the FIG., the x-axis sliding lower plate 655 iscoupled to the gripper's first component (via by support frame 644) byrails, so as to permit relatively frictionless x-axis displacement ofthe assembly upper plate 653, the pivot shaft 651, the vacuum chuck 643and the gripper's second component 635 on a general basis relative tocomponent 633 (and support frame 644), all while at the same timeconstraining these two components 633/635 to move together in they-dimension. This structure provides mechanical support for a floatingpivot point, with common-mode and differential-mode voice coildisplacements being used, to respectively provide error-mitigatingoffsets of the second component along the direction of arrows 673 androtation arrows 675. Note that a floating pivot point is not requiredfor all embodiments, e.g., in embodiments where the transducer providessufficient output impedance, a mechanical pivot mechanism can bepotentially omitted. Whether a mechanical support structure is used ornot, a floating pivot point advantageously permits common-mode anddifferential-mode control over multiple transducers, so as to repositiona substrate in x and θ dimensions, and so approximate a “straight edge”ideal transport path; various modifications and alternatives will nodoubt occur to those of ordinary skill in the art.

FIG. 6E provides a schematic view 681, which illustrates elements of thepivot mechanism represented by FIGS. 6B-6D. More specifically, this FIG.now illustrates a linear x-axis rails 683 which effectively provide abearing 685 on either side of the x-axis sliding lower plate 655 topermit that structure (and everything supported above it) to ride intoand out of the drawing page. At the same time, the assembly upper plate653 mounts a bushing 686 so as to permit free rotation of that platerelative to the x-axis siding lower plate 655 about pivot axis 649. Morespecifically, the bushing 686 supports bearings 689 to permit thisrotation. FIG. 6E also illustrates the flexure provided by the assemblyupper plate 653, relative to the gripper's second component 635 andtransducers 637/639.

While the transducer correction mechanisms depicted in FIGS. 6A-6D havebeen exemplified in the context of a gripper assembly, the same basicstructure can also be used for the printhead assembly (or for eachprinthead assembly or other tool carrier). Specifically, a firstcomponent rides a track (or x-axis carriage assembly) atop a gasbearing, while a second component carrying printheads (or other tools)is displaced in a “y” and/or “z” dimension as a function of positionalerror in that dimension as a function of x-axis position (and/or otherfactors, e.g., temperature). For correction in a given dimension, twotransducers are again used with a virtual or floating pivot point toeffectuate both y and θ corrections (or z and xz-plane angularcorrection) in relative position of a printhead relative to a substrate,and in so doing, cause the printhead to follow a virtual straight edgepath. Optionally using two such correction mechanisms together, toprovide straight edge paths for each the gripper and printheadconveyance system, respectively, one may effectively provide for a veryprecise, regular print grid which provides for greater precision overdroplet placement. Z-axis adjustment of the printhead can also becontrolled using a transducer-based motion correction system of similardesign, to provide for corrections in height of a printhead orificeplate relative to a substrate surface, and thereby manage heightdifference to also have improved precision. Other degrees of freedom mayalso be corrected in this manner. In a precision motion system,especially a printer based fabrication system, where a coordinatereference system used for printing/manufacture is effectively tied tomultiple transport paths, the use of plural correction systems of thistype improves precision over droplet landing location and thusfacilitates greater uniformity in fabricated layers; in turn, this makesit easier to produce thinner layers, e.g., having thicknesses of fivemicrons or less. It again bears noting that although the designsdiscussed above emphasize the use of a “virtual straight edge,” forpurposes of improving print grid regularity, all embodiments are not solimited, and nearly any desired “ideal” path can be approximated usingthe teachings provided here.

IV. Various Use Cases, Revisited

FIGS. 7A-7I are used to revisit a number of specific use cases relativeto the techniques introduced above.

More specifically, FIG. 7A shows an embodiment 701 where an opticalguide 702 is used to ensure straight motion of a gripper 703 andsubstrate 704. The depicted structure implements a continuous processwhich is performed in real time. A robotic gripper (not shown) holds thesubstrate as it is advanced in the conveyance system; in the depictedembodiment, the optical beam 702 (i.e., a beam produced by a lasersource 705) ideally remains parallel to the substrate and at a constantdistance therefrom as the latter is advanced through the system (this isrepresented by virtual straight edge 711). To the extent that deviationoccurs, the offset (in linear position) and rotation of the gripper'ssecond component relative to the beam 702 is measured by two lasersensors 706A/706B. Path deviation measurements from the two lasersensors enable two actuators 707A/707B (e.g., piezoelectric transducers,voice coils, etc.) to adjust the rotation angle 709 (about an optionalmechanical pivot assembly 708) and linear position 710 along a directionorthogonal to the beam, so as to preserve the “ideal” relationshipbetween the gripper's second (offsettable) component and the beam.

FIG. 7B shows another embodiment 713, but this time where a laser sourceand/or optics 714 are mounted in fixed relationship to the “thing” beingtransported and where a sensor 715 is stationary. Differential readingsover time from the sensor for example can be used to detect and correctrotation error and steady state beam misalignment can be used to detectand correct linear position of the thing being transported in adirection orthogonal to a beam 716. As indicated by dashed extensionline 717, one variation of this configuration features the laser sourcestationary, such that a beam is directed along line 717 to thetransported item and is redirected by optics 714 mounted to theoffsettable component to the sensor in a way that permits detection ofdeviation from the desired path. Many variations will occur to thosehaving skill in the art, e.g., any mechanism where a light or otherradiation source, a beam, a detector, and so forth are used to detectpositional deviation are contemplated; without limitation in otherembodiments, both the laser source and detector can be stationary whileoptics (such as flat or curvilinear mirrors or beam splitters) aremounted in a manner fixed relative to the offsettable component, in amanner to promote detection of positional deviation. Whichever design isused, signals from the sensor(s) are once again used to direct actuators718A/718B so as to maintain alignment of the beam.

FIG. 7C shows an embodiment 719 where a sensor 720 is used to calibratea light source 721, e.g., so as to detect and/or correct for path error722 relative to an intended path 723. A laser sensor near the lasersource is used to optically measure the laser beam direction. If thelaser beam direction deviates from the intended path 723, then positionof the laser and/or deflection of its beam is adjusted (manually and/orelectronically, under the influence of an electronic control signal)until the intended path is achieved. For example, in one embodiment, alaser mount can be controlled by piezoelectric (or other) transducers orother deflection means 724 (under the influence of processing circuitry725) to adjust inclination and/or rotation of the laser source untilproper alignment is obtained. Note that advantageously, the laser sensorcan be designed to detect path deviation in two dimensions, to ideallyeffect correction of alignment errors using an automated control loopwith a response within milliseconds. Note also that design of a suitablelaser sensor is within the level of one of ordinary skill in the art,e.g., in some embodiments, a beam-splitter and four-cell sensor can beused to align the beam, as referenced earlier; many suitable adjustmentand sensing mechanisms will occur to those having skill in optics,including without limitation, those based on analog designs (e.g., ananalog output is produced with voltage proportional to position ordeviation), convex or concave mirrors and beam splitters,interferometry, and other mechanisms.

FIG. 7D shows another embodiment 727 where a light source 728 isimproperly aligned; unlike the embodiment of FIG. 7C, however, deviationbetween an erroneous optical path 729 and a correct optical path 730 ismitigated passively and electronically, e.g., by using a first sensors731 to detect error and actuators 732A/732B to perform compensatingoffsets. Signals to control these offsets can be stored in digitalmemory 733 and retrieved during system operation or otherwise added todynamic corrections (identified at run time from second sensors734A/734B) as a function of transport path position, such that atransported object follows the correct path 730. FIG. 7D shows an addedlaser position sensor 731 on the left near the end of the laser beam.This sensor allows one to remove the sensor 720 (and associated activelaser attitude control, represented in FIG. 7C); that is, instead ofactively compensating for laser alignment error, the error is measuredby the added laser sensor 731 and corrected using two transducers (i.e.,while moving the substrate, as a function of substrate position).

FIG. 7E shows an embodiment 735 that implements a zero-target controlloop; sensors 736A/736B dynamically detect deviation from a desired pathin one or more dimensions (in this case represented by deviation between“cross-hairs” 737A/737B and a beam 738 from a laser source 739);processing electronics 740A/740B preprocess outputs from the sensorssuch that a zero signal is the norm (indicating “no adjustment”); thisoutput is provided to a motion controller (i.e., a processor-implementedzero-target controller) 741, which generates correction signals toprovide feedback to drive transducers 742A/742B when correction isrequired, i.e., so as to always drive error to zero. FIG. 7E does notexplicitly show which method is used for correcting for laser alignmenterror, but without limitation, either the active control methodintroduced relative to FIG. 7C or the transducer-compensation methodrepresented by FIG. 7D can be used for this purpose; other methodologieswill occur to those having skill in the art.

FIG. 7F shows an embodiment 745 where actuators 746A/746B are driven tomaintain a transported object (e.g., a gripper 747 and/or substrate 748)as always level in terms of z-axis height relative to a beam or opticalguide 749. In this case, sensors 750A/750B detect deviation of thegripper (or other conveyance mechanism) from the optical guide 749, anddrive the two actuators 746A/746B to equalize jitter in height or tootherwise precisely control height (e.g., to maintain a predeterminedheight profile such as to match zones as referenced earlier). Aprocessor-based motion controller 751 can once again be used to assistwith this purpose.

FIG. 7G shows an embodiment 755 which uses two parallel conveyancesystems 756A/756B for a given direction of transport. In this case,whether due to size of the substrate being received or due to otherspecifics of the manufacturing process, it is assumed that a substrateor other transported element 758 is to be transported by multipletraveling components along parallel conveyance paths, and that it isdesired that each conveyance system (i.e., each one two parallel vacuumgripper systems in this example) be controlled exactly in sync to avoidmechanical jitter and/or substrate skew. To this end, each of theparallel conveyance systems 756A/756B has its own optical guide or beam757A/757B and transducer compensation system 759A/759B, each generallycorresponding to one of the embodiments described herein. Sensor pairs761A/761B and 762A/762B report signals to motion controller circuitry763 which controls two motors (not shown), one corresponding to eachconveyance system 756A/756B. One of the conveyance systems 7566 alsomounts another light source 765 (e.g., a laser source), which generatesyet a third optical guide 766, while the other conveyance system 756Amounts a third sensor 767, e.g., a four cell design as describedearlier. As shown in phantom lines, path deviation signals from each ofthe five sensors 761A/761B/762A/762B and 767 are fed to the motioncontroller circuitry, which advances or retards one or both of themotors so that each of the parallel conveyance system 756A/756B isadvanced exactly in parallel. For embodiments that use multipletransducer correction systems (e.g., to control both x offset and zheight, for each of lateral displacement and/or fly height control), thethird optical guide 766 and signal from the third sensor can be used todetect height differential between the second, offsettable component(i.e., of each gripper system in this embodiment). Just as was the casewith FIGS. 7C-D, the components associated with the third optical guidecan optionally further include components used during a calibration modeor process to ensure that the third optical guide is level and isorthogonal to the direction of transport provided by the parallelconveyance systems 756A/756B.

FIG. 7H shows an embodiment 771 where two conveyance systems 772 and 773used for orthogonal transport paths each have their own respective lasersource 774/775 and associated optical guide 777/778 and motioncontroller 780/781. The result is that errors are correctedtransparently to general system motion control, such that each motioncontroller 780/781 can receive respective drive signals or commandsignals 782/783, i.e., as absolute position commands, to establishproper position relative to a system coordinate reference system.

FIG. 7I shows an embodiment 787 where two conveyance systems 788/789each have their own source 790/791 and sensor pairs 792A/792B and793A/793B, but where only one conveyance system has actuators 794A/794Bto correct for motion jitter; in this case, a motion controller 795generates transducer control signals 796A/796B so that actuators794A/794B are driven to compensate for error associated with otherconveyance system 788, as was introduced above in connection with thediscussion of FIG. 3E. Non-motion errors, such as error in alignment ofthe optical guide for either conveyance system and/or non-orthogonalitybetween the conveyance systems can also be corrected, as introducedearlier (this non-orthogonality is represented by two depicted erroneousbeam paths 797A/797B). As denoted by respective correction signals798A/798B sent to each laser source 790/791, one or both optical sourcescan be calibrated electronically (or by mixing any of the optionalalignment/calibration techniques introduced earlier) to correct fornon-orthogonality, for example, by realigning laser paths, adjustingcorrection signals provided to actuators 794A/794B, and so on.

Note that while a variety of options and use cases have been describedabove, it should be noted that the various techniques and options shouldbe viewed as optional and capable of being mixed and matched with eachother in any permutation or combination. As a non-limiting example, itis possible (and is expressly contemplated) that one may use azero-target controller (and associated “crosshair” sensors, introducedabove in connection with the embodiment shown in FIG. 7E) in theembodiment of FIG. 7H. Other combinations, permutations andmodifications will no doubt be apparent to those having ordinary skillin the art, which are similar to one or more of the examples discussedabove.

V. Multi-Dimensional Control of an Offsettable Conveyance SystemComponent

One embodiment of a gripper error correction system, as noted above, cancorrect for error in multiple dimensions that are orthogonal to aconveyance path and/or orthogonal to an optical guide. As exemplifiedabove, in an environment where a conveyance system moves a transportedcomponent along a first translational axis (e.g., along the “y” axis ofmotion), a set of one or more actuators or transducers, such as voicecoils or piezoelectric transducers can be used to offset the transportedcomponent along a second translational axis (e.g., along the “x” axis ofmotion), while a set of one or more actuators or transducers, such asvoice coils or piezoelectric transducers can be used to offset thetransported component (or another component) along a third translationalaxis (e.g., along the “z” axis of motion), with all three of these axesbeing orthogonal to one another. In another embodiment, three or moreactuators can be used for each offsettable component, so as tofacilitate levelization of that component. These various design optionswill be discussed below in connection with FIGS. 8A and 8B.

FIG. 8A is a cross-sectional view of an assembly 801 that uses twodifferent sets of transducers “T” to correct for error in two or moredimensions. More specifically, a first, track-guided component 803 of aconveyance system travels along a first dimension of travel (i.e., alongthe “y” axis in this example, into the drawing page) while a second,offsettable component 805 is constrained to travel with the firstcomponent along the first dimension of travel. The depicted assembly hastwo transducer sets, including set 807, which is seen to havetransducers to displace the second component relative to the firstcomponent along the “x” axis, much as described in connection with thegripper embodiments discussed above, and a second set 809, which is seento have transducers to displace the second component relative to thefirst component along the “z” axis, to adjust fly height. In thisexample, the second transducer set is seen to optionally have threetransducers and associated contact points c1-c3, to permit automatedplanar levelization of the second component 805 along the “z” axis(i.e., to adjust unintended tilt of the second component in xz and yzplanes). As denotes by numeral 805′ and broken linkage 806, the secondcomponent optionally can be structured as two or more components, e.g.,so as to be offsettable from each other along the “z” axis andoffsettable as a group from the first component along the “x” axis. Eachtransducer set is seen to include a mechanical linkage/support structure(labeled “M” in the figure), such as the floating pivot plate assemblydescribed earlier or a structural support analogy, so as structurallyconstrain components 803 and 805 to move with each other along the “y”axis while permitting offsettable component 805 to travel in x and zdimensions relative to the first component 803.

FIG. 8B is a cross-sectional view of another assembly 831 that uses twodifferent sets of transducers “T” to correct for error in two or moredimensions. In this figure, a first component is represented by numeral833 while a second offsettable component is represented by numeral 835;these components in this example also are constrained to travel togetheralong the “y” axis, while being selectively offsettable from one anotherin the direction of arrows 836 (i.e., along the “x” axis). In oneembodiment, these components are structurally identical to the gripperdesign of FIG. 6B, with a set of transducers used to effectuatedisplacement in the direction of arrows 836 and mechanical linkagebetween components 833 and 835 not being visible in the figure.

To correct for fly height in this example, the second component 835supports a vacuum chuck 839 which is once again used to engage asubstrate, represented by dashed line 845. One or more transducers 837are used to selectively displace the vacuum chuck 839 along the “z”axis, in the direction of arrows 841. In this case, the vacuum chuck 839is also supported by a flexure 843 which provides spring force to permitslightly negative “z” axis displacement of the vacuum chuck 839 andsubstrate 845 when no force is exerted by the one or more transducers839, but which also provides sufficient spring force so as to permitslightly positive “z” axis displacement of the vacuum chuck 839 and thesubstrate 845 when the transducers are actuated to their full throws;depending on embodiment, the transducers can be piezoelectrictransducers when the required throws are less than about 3 microns,while voice coils or similar transducers can be used for larger throws,e.g., five microns or more. Other types of actuators can also be used,depending on embodiment.

While in this example a flexure is used to provide structural supportthat constrains the two components to travel together along the “y”axis, along with floating pivot assembly (e.g., as seen in FIG. 6D),other types of structures performing these functions will no doubt occurto those having ordinary skill in mechanics; the examples presentedabove are consequently to be viewed as illustrative only, and notlimiting.

VI. Conclusion

Reflecting on the various techniques and considerations introducedabove, a manufacturing process can be performed to mass produce productsquickly and at low per-unit cost. Applied to display device or solarpanel manufacture, e.g., flat panel displays, these techniques enablefast, per-panel printing processes, with multiple panels optionallyproduced from a common substrate. By providing for fast, repeatable,error-free printing techniques (e.g., using common inks and printheadsfrom panel-to-panel), it is believed that printing can be substantiallyimproved, for example, reducing per-layer printing time to a smallfraction of the time that would be required without the techniquesabove, all while guaranteeing precision deposition of ink on aconsistent basis within a desired target area of each substrate. Againreturning to the example of large HD television displays, it is believedthat each color component layer can be accurately and reliably printedfor large substrates (e.g., generation 8.5 substrates, which areapproximately 220 cm×250 cm) in one hundred and eighty seconds or less,or even ninety seconds or less, representing substantial processimprovement. Improving the efficiency and quality of printing paves theway for significant reductions in cost of producing large HD televisiondisplays, and thus lower end-consumer cost. As noted earlier, whiledisplay manufacture (and OLED manufacture in particular) is oneapplication of the techniques introduced herein, these techniques can beapplied to a wide variety of processes, computer, printers, software,manufacturing equipment and end-devices, and are not limited to displaypanels. In particular, it is anticipated that the disclosed techniquescan be applied to any process where a printer is used to deposit a layerof multiple products as part of a common print operation, includingwithout limitation, to many microelectronics applications.

Note that the described techniques provide for a large number ofoptions. In one embodiment, panel (or per-product) misalignment ordistortion can be adjusted for on a product-by-product basis within asingle array or on a single substrate. A printer scan path can beplanned without need for adjustment/adaptation based on one or morealignment errors, such that misorientation of a substrate (or othertransported item, such as a printhead) is automatically compensated forvia transducers which couple a substrate and conveyance system (e.g., agripper). In one embodiment, transducer correction can be used tomitigate error in a different transport path (e.g., a printheadtransport path), or multiple transducers or transducer sets can be usedto correct for multidimensional position and/or orientation error. Invarious embodiments, as mentioned, error is not premeasured, but rather,is detected dynamically and used to fine tune substrate and/orindividual panel position so as to provide for perfect alignment.

Also, while various embodiments have illustrate the use of a gripper (ormechanism to couple the substrate to a conveyance mechanism), and theuse of two transducers to effectuate fine tuning, other embodiments canuse different numbers of these elements. For example, in one embodiment,two or more grippers can be used, each having their own, dedicatedtransducers. In addition, while the techniques described above have beenexemplified as applied to a printer that uses a vacuum gripper system,many other applications can benefit from the described techniquesincluding applications that use a different type of conveyancemechanism, a different type or printer, a different type of depositionmechanism, or another type of transport path or mechanism. Clearly, manyvariations exist without departing from the inventive principlesdescribed herein.

The foregoing description and in the accompanying drawings, specificterminology and drawing symbols have been set forth to provide athorough understanding of the disclosed embodiments. In some instances,the terminology and symbols may imply specific details that are notrequired to practice those embodiments. The terms “exemplary” and“embodiment” are used to express an example, not a preference orrequirement.

As indicated, various modifications and changes may be made to theembodiments presented herein without departing from the broader spiritand scope of the disclosure. For example, features or aspects of any ofthe embodiments may be applied, at least where practical, in combinationwith any other of the embodiments or in place of counterpart features oraspects thereof. Thus, for example, not all features are shown in eachand every drawing and, for example, a feature or technique shown inaccordance with the embodiment of one drawing should be assumed to beoptionally employable as an element of, or in combination of, featuresof any other drawing or embodiment, even if not specifically called outin the specification. Accordingly, the specification and drawings are tobe regarded in an illustrative rather than a restrictive sense.

We claim:
 1. A method of fabricating a thin-film layer, the methodcomprising: controlling a conveyance system to provide relativetransport between a material source and a substrate along a conveyancepath, wherein during the relative transport, the substrate is to besupported by a support structure and the material source is to deposit amaterial onto the substrate in order to form the thin-film layer;providing an optical source to form an optical beam and providing anoptical detector fixed in position relative to at least one of thematerial source or the substrate; causing the optical detector to detectdivergence of the position of the optical detector from the optical beamduring the relative transport, and responsively generate an output; anddriving at least one transducer to displace at least one of the materialsource or the detector relative to the conveyance path, in dependence onthe output, so as to cause the position of the optical detector toremain coincident with the beam during the relative transport.
 2. Themethod of claim 1, wherein the method further comprises forming anelectronic product from the substrate, the electronic product comprisingthe thin-film layer.
 3. The method of claim 1, wherein the conveyancesystem comprises a gripper that is to selectively engage the substrateand transport the substrate along the conveyance path, and wherein themethod further comprises driving the at least one transducer during therelative transport so as to cause the substrate to travel a straightline relative to the optical beam for at least a portion of theconveyance path.
 4. The method of claim 3, wherein the material sourcecomprises a printhead, wherein the method further comprises causing theprinthead is to deposit a liquid ink onto the substrate, the material tobe supplied to the substrate by the liquid ink and comprising afilm-forming substance, and wherein the method further comprisesprocessing the liquid ink following deposition onto the substrate so asto solidify the film-forming substance relative to the liquid ink, toform the thin-film layer, using at least one of a (1) a radiation sourceto cure the film-forming substance to form the thin-film layer, or a (2)a heat source to evaporate solvent from the liquid ink to cause thefilm-forming substance to form the thin-film layer.
 5. The method ofclaim 2, wherein the optical source is a laser and the optical beam is alaser beam oriented in a manner parallel to the conveyance path, andwherein the method further comprises using the laser beam as a virtualguide, and driving the at least one transducer so as to correct fordeviation between the virtual guide and the conveyance path.
 6. Themethod of claim 1, wherein: the support structure comprises a floatationtable; the method further comprises using the floatation table toprovide a gas cushion; the conveyance system comprises a vacuum gripperthat is to use a vacuum to selectively engage the substrate; and themethod further comprises selectively engaging the substrate with thevacuum gripper and pulling the substrate along the conveyance path atopthe gas cushion with the vacuum gripper during the relative transport.7. The method of claim 6, wherein the at least one transducer comprisesa voice coil having a linear throw which is oriented in a directionindependent to a direction of the optical beam.
 8. The method of claim7, wherein the direction of the linear throw is normal to a surface ofthe substrate, and wherein the method further comprises using the linearthrow to adjust a height of the substrate relative to the supportstructure.
 9. The method of claim 7, wherein the direction of the linearthrow is parallel to the surface of the substrate, and wherein themethod further comprises using the linear throw to adjust a distancebetween the substrate and the transport path.
 10. The method of claim 7,wherein: the conveyance system comprises a track; the gripper comprisesa first part, which travels along the track, and a second part, whichmounts the optical detector and the vacuum gripper; the voice coilcouples the first part with the second part; and the gripper furthercomprises a mechanical linkage between the first part and the secondpart; and the method further comprises advancing the first part alongthe track during the relative transport, and using the mechanicallinkage to constrain the second part to travel with the first part in adirection of the conveyance path during the travel of the first partalong the track, while permitting the displacement of the second partrelative to the first part by the voice coil, toward and away from thetrack.
 11. The method of claim 1, wherein the substrate is a firstsubstrate and the method is to fabricate the thin-film layer on eachgiven substrate of a series of substrates, including the firstsubstrate, wherein each given substrate of the series of substratesfeatures at least one fiducial, and wherein the method furthercomprises: using a camera to image the fiducial of each given substrateof the series of substrates, including the first substrate; mechanicallypositioning each given substrate of the series of substrates relative tothe conveyance path, so as to align each given substrate of the seriesof substrates relative to the conveyance path; and causing the vacuumgripper to engage each given substrate of the series of substrates forthe relative transport following the alignment of the given substrate ofthe series of substrates relative to the conveyance path.
 12. The methodof claim 1, wherein the at least one transducer comprises twotransducers, each having a linear throw that is parallel to a surface ofthe substrate, and wherein the method further comprises driving the twotransducers in common-mode to displace the substrate in a directionperpendicular to the conveyance path and in differential-mode to rotatethe substrate relative to the conveyance path.
 13. The method of claim1, wherein the at least one transducer comprises a piezoelectrictransducer.
 14. The method of claim 1, wherein the conveyance path ischaracterized by mechanical imperfections, and wherein the methodfurther comprises using optical beam, the optical detector and the atleast one transducer to cause the relative transport to follow astraight line notwithstanding the mechanical imperfections.